08/10/2011 - Speed of light 'broken' at CERN, scientists claim
It was Albert Einstein, no less, who proposed more than 100 years ago that nothing could travel faster than the speed of light.
But last night it emerged that the man who laid the foundations for the laws of nature may have been wrong.
The science world was left in shock when workers at the world’s largest physics lab announced they had recorded subatomic particles travelling faster than the speed of light
If the findings are proven to be accurate, they would overturn one of the pillars of the Standard Model of physics, which explains the way the universe and everything within it works.
Einstein’s theory of special relativity, proposed in 1905, states that nothing in the universe can travel faster than the speed of light in a vacuum. But researchers at the CERN lab near Geneva claim they have recorded neutrinos, a type of tiny particle, travelling faster than the barrier of 186,282 miles (299,792 kilometers) per second.
The results have so astounded researchers that American and Japanese scientists have been asked to verify the results before they are confirmed as a discovery.Antonio Ereditato, spokesman for the researchers, said: “We have high confidence in our results. We have checked and rechecked for anything that could have distorted our measurements but we found nothing.”
Scientists agree if the results are confirmed, that it would force a fundamental rethink of the laws of physics.
John Ellis, a theoretical physicist, said Einstein’s theory underlies “pretty much everything in modern physics”.
But last night it emerged that the man who laid the foundations for the laws of nature may have been wrong.
The science world was left in shock when workers at the world’s largest physics lab announced they had recorded subatomic particles travelling faster than the speed of light
If the findings are proven to be accurate, they would overturn one of the pillars of the Standard Model of physics, which explains the way the universe and everything within it works.
Einstein’s theory of special relativity, proposed in 1905, states that nothing in the universe can travel faster than the speed of light in a vacuum. But researchers at the CERN lab near Geneva claim they have recorded neutrinos, a type of tiny particle, travelling faster than the barrier of 186,282 miles (299,792 kilometers) per second.
The results have so astounded researchers that American and Japanese scientists have been asked to verify the results before they are confirmed as a discovery.Antonio Ereditato, spokesman for the researchers, said: “We have high confidence in our results. We have checked and rechecked for anything that could have distorted our measurements but we found nothing.”
Scientists agree if the results are confirmed, that it would force a fundamental rethink of the laws of physics.
John Ellis, a theoretical physicist, said Einstein’s theory underlies “pretty much everything in modern physics”.
08/10/2011 - Churning galaxy is a snake pit
A pit of writhing snakes — that’s what the first picture of turbulent gas in our Milky Way looks like. Bryan Gaensler from the University of Sydney, Australia, and his team used a CSIRO radio telescope in eastern Australia to make the groundbreaking image. The space between the stars in our galaxy is not empty, but is filled with thin gas that continually swirls and churns. “This is the first time anyone has been able to make a picture of this interstellar turbulence,” said Gaensler. “People have been trying to do this for 30 years.”
Turbulence makes the universe magnetic, helps stars form, and spreads the heat from supernova explosions through the galaxy. “We now plan to study turbulence throughout the Milky Way,” Gaensler said. “Ultimately this will help us understand why some parts of the galaxy are hotter than others, and why stars form at particular times in particular places.”
Gaensler and his team studied a region of our galaxy about 10,000 light-years away in the southern constellation Norma. They used CSIRO’s Australia Telescope Compact Array because “it is one of the world’s best telescopes for this kind of work,” said Robert Braun from CSIRO Astronomy and Space Science.
The radio telescope was tuned to receive radio waves that come from the Milky Way. As these waves travel through the swirling interstellar gas, one of their properties — polarization — is slightly altered, and the radio telescope can detect this. Polarization is the direction the waves “vibrate.” Light can be polarized: Some sunglasses filter out light polarized in one direction while letting through other light.
The researchers measured the polarization changes over an area of sky and used them to make a spectacular image of overlapping entangled tendrils, resembling writhing snakes. The “snakes” are regions of gas where the density and magnetic field are changing rapidly as a result of turbulence.
The “snakes” also show how fast the gas is churning — an important number for describing the turbulence. Team member Blakesley Burkhart from the University of Wisconsin-Madison made several computer simulations of turbulent gas moving at different speeds. These simulations resembled the snakes’ picture, with some matching the real picture better than others. By picking the best match, the team concluded that the speed of the swirling in the turbulent interstellar gas is around 43,500 mph (70,000 km/h) — relatively slow by cosmic standards.
08/10/2011 - Kepler planet circles
two suns
The first confirmed example of a planet orbiting two suns has been found in the Kepler dataset.
Kepler-16b is a gaseous world similar to Saturn in terms of size and mass and experiences a surface temperature dipping to
-100 degrees Celsius so it is unlikely to host life, but Kepler scientist and lead author of the study Laurance Doyle says that doesn't necessarily rule out other double star planets as places to look for life in the future.
"The habitable zone would not be like anything we presently know," he says. "We usually think of the habitable zone as a spherical shell around the star at a certain radius. But with two stars orbiting around each other in the middle of the stellar system, the habitable zone would be variable as the stars changed their distances from the planets."The Kepler spacecraft detected the planet using the transit method, that is, looking for the periodic dimming in a star as a planet moves across its face, temporality blocking out some of its light. The detection of Kepler-16b was complicated by the fact that the two stars in the system also eclipsed each other, but since the stars' brightness dropped even when the stars were not in eclipse, the presence of a third body was inferred. The additional observation that the dimming events occurred at irregular time intervals meant that the stars were in different positions in their orbit each time the third body passed, showing that it was circling both stars.
"I was hoping to find a circumbinary planet in the Kepler data, but Kepler-16 is better than anyone imaged," Doyle tells Astronomy Now. "The orbits are so exquisitely aligned – the stars with each other and the planet with them – that we have been able to determine the size and mass of each of the stars and planet with unprecedented accuracy."
Both stars are smaller and cooler than our own Sun, and are orbited by Kepler-16b once every 229 days at a distance of 65 million miles. Follow-up observations by the Tillinghast Reflector Echelle Spectrograph (TRES) on the 60-inch telescope at the Smithsonian Astrophysical Observatory’s Whipple Observatory in Arizona revealed that the two stars orbit each other every 41 days at an average distance of 21 million miles.
Doyle reveals that there are "some good candidates" for further circumbinary planets in the Kepler dataset. "Now that we know how to find them, I think we are going to have quite a few more in the next several months," he adds.
08/10/2011 - Powerful new telescope array opens eyes on Universe
A crucial step for the world’s most powerful ground-based telescope array, the Atacama Large Millimeter/submillimeter Array (ALMA) took its first science observations this weekend, of the colliding Antennae galaxies.
Currently comprising twenty working 12-metre antennas – the first image was constructed using sixteen – the final array, set for completion by 2013, will boast 66 telescopes. At a grueling 5,000 metres altitude on the Chajnantor plain of the Chilean Andes, ALMA is located at one of the highest and driest astronomical sites in the world, affording exceptional atmospheric conditions for making millimeter and submillimeter wavelength observations. These long wavelengths allow astronomers to study extremely cold objects in space, such as the dense clouds of cosmic dust and gas from which stars and planets form, as well as very distant objects in the early Universe, and the relic radiation left over from the big bang.
“We are exploring an extremely important part of the Universe, which was previously hidden,” Diego Garica-Appadoo, an ALMA astronomer said from the array’s control room yesterday.
The first image, taken on Friday and released today is part of the science verification phase, that is, to check that the array is working correctly and able to reproduce already well-studied objects. It depicts the Antennae galaxies, the site of an intergalactic smash-up between two spiral galaxies. During galactic crashes the stars themselves avoid collision, but if there are clouds of gas present these plough into each other, causing them to become compressed and triggering the formation of millions of new stars. While visible light images typical of the Hubble Space Telescope shows the stars in the galaxies, ALMA’s long wavelength eyes reveal the dense gas from which these new stars are born.
“What the ALMA image shows is exactly where the gas clouds are, which are still in process of forming more stars,” Richard Hills, ALMA Project Scientist tells Astronomy Now. “Once the image has been studied in detail we will learn about the speeds at which the clouds are coming together, the size of the clouds the amounts of gas in the clouds – generally the nitty gritty of what actually happens when two galaxies collide.”Once complete, the main array will comprise fifty 12 metre antennas, with a compact array made up of twelve 7-metre and four 14-metre antennas. The maximum separation of the antennas will be 16 kilometres, more than a thousand times the diameter of a single individual telescope within the array. Increasing the separation between the antennae will result in sharper images, while increasing the number of antennas linked up for any observation will provide more detailed images.
Observations in this early science phase will continue while the array is being completed; around 100 projects out of the 900 submitted by astronomers worldwide have been accepted for this phase, and will cover topics from the study of young stars and the hunt for water in their debris discs to provide insight into the formation of our own Solar System, to studies of the flaring episodes of the supermassive black hole that lurks in the centre of our Milky Way to learn more about its feeding habits as it consumes nearby material.
“Even now with just 16 antenna we are seeing things we haven’t been able to before, but even though we know what we want to study, it’s all the things that we don’t know are out there that are going to be the most interesting,” adds Garica-Appadoo.
08/09/2011 - The star that should not exist
A team found that the proportion of metals in the star is more than 20,000 times smaller than that of the Sun.
A faint star in the constellation Leo the Lion, called SDSS J102915+172927, has been found to have the lowest amount of elements heavier than helium — what astronomers call “metals” — of all stars yet studied. It has a mass smaller than that of the Sun and is probably more than 13 billion years old.
“A widely accepted theory predicts that stars like this, with low mass and extremely low quantities of metals, shouldn’t exist because the clouds of material from which they formed could never have condensed,” said Elisabetta Caffau from University of Heidelberg, Germany, and the Observatory of Paris, France. “It was surprising to find, for the first time, a star in this ‘forbidden zone,’ and it means we may have to revisit some of the star formation models.”
The team analyzed the properties of the star using the X-shooter and UVES instruments on the Very Large Telescope (VLT) in Atacama, Chile. This allowed them to measure how abundant the various chemical elements were in the star. They found that the proportion of metals in SDSS J102915+172927 is more than 20,000 times smaller than that of the Sun.
“The star is faint and so metal-poor that we could only detect the signature of one element heavier than helium — calcium — in our first observations,” said Piercarlo Bonifacio from the Observatory of Paris. “We had to ask for additional telescope time from The European Southern Observatory’s (ESO) director general to study the star’s light in even more detail, and with a long exposure time, to try to find other metals.”
Cosmologists believe that the lightest chemical elements — hydrogen and helium — were created shortly after the Big Bang, together with some lithium, while almost all other elements were formed later in stars. Supernova explosions spread the stellar material into the interstellar medium, making it rich in metals. New stars form from this enriched medium, so they have higher amounts of metals in their composition than the older stars; therefore, the proportion of metals in a star tells us how old it is.
“The star we have studied is extremely metal-poor, meaning it is very primitive,” said Lorenzo Monaco from ESO. “It could be one of the oldest stars ever found.”
Also very surprising was the lack of lithium in SDSS J102915+172927. Such an old star should have a composition similar to that of the universe shortly after the Big Bang, with a few more metals in it. But the team found that the proportion of lithium in the star was at least 50 times less than expected in the material produced by the Big Bang.
“It is a mystery how the lithium that formed just after the beginning of the universe was destroyed in this star,” Bonifacio added.
The researchers also point out that this freakish star is probably not unique. “We have identified several more candidate stars that might have metal levels similar to, or even lower than, those in SDSS J102915+172927. We are now planning to observe them with the VLT to see if this is the case,” said Caffau.
08/09/2011 - Rare martian lake delta spotted by Mars Express
The delta structure provides a clear indication that liquid water flowed across the surface of Mars in the planet’s early history.
The European Space Agency’s (ESA) Mars Express has spotted a rare case of a crater once filled by a lake, revealed by the presence of a delta. The delta is an ancient fan-shaped deposit of dark sediments laid down in water. It is a reminder of Mars’s past, wetter climate.
The delta is in the Eberswalde Crater in the southern highlands of Mars. The 40-mile-diameter (65 kilometers) crater is visible as a semicircle on the right of the image and was formed more than 3.7 billion years ago when an asteroid hit the planet.
The rim of the crater is intact only on its right-hand side. The rest appears only faintly or is not visible at all. A later impact created the 87-mile-diameter (140 km) Holden Crater that dominates the center and left side of the image. The expulsion of large amounts of material from that impact buried parts of Eberswalde.
However, within the visible part of Eberswalde, the delta and its feeder channels are well preserved, as seen near the top right of the crater. The delta covers an area of 44 square miles (115 square km). Small, meandering feeder channels are visible toward the top of the crater, which would have filled it to form a lake.
After the deposition of the delta sediments in the crater’s ancient lake, fresher sediments accumulated to cover up a major part of both the channels and the delta. These secondary sediments, presumably deposited by the wind, were later eroded in the delta area, exposing an inverted relief of the delta structure.
This delta structure, first identified with NASA’s Mars Global Surveyor spacecraft, is characteristic of the presence of a lake in the crater at that time. Such features provide a clear indication that liquid water flowed across the surface of Mars in the planet’s early history.
Both Eberswalde Crater and Holden Crater were on the list of four possible destinations for the next NASA Mars rover to be launched late this year. The main objective of the Mars Science Laboratory mission is the search for present or previously habitable environments on Mars. ESA’s Mars Express mission has been helping in the search for the best landing site.
Eberswalde was proposed because its delta indicates the long-lasting presence of liquid water in the past, and Holden Crater was a candidate because of its mineral diversity and many structures that again suggest past liquid water. Another candidate, Mawrth Vallis, exposes some of the oldest clay-rich layers on Mars. However, in July, Gale Crater, the final entry on the list, was selected as the mission’s landing site, given its high mineral and structural diversity related to water.
Eberswalde, Holden, and Mawrth Vallis will get to hold on to their secrets for a while longer.
08/09/2011 - Chandra Finds Nearest Pair Of Supermassive Black Holes
Astronomers using NASA's Chandra X-ray Observatory discovered the first pair of supermassive black holes in a spiral galaxy similar to the Milky Way. Approximately 160 million light years from Earth, the pair is the nearest known such phenomenon.
The black holes are located near the center of the spiral galaxy NGC 3393. Separated by only 490 light years, the black holes are likely the remnant of a merger of two galaxies of unequal mass a billion or more years ago.
"If this galaxy wasn't so close, we'd have no chance of separating the two black holes the way we have," said Pepi Fabbiano of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., who led the study that appears in this week's online issue of the journal Nature. "Since this galaxy was right under our noses by cosmic standards, it makes us wonder how many of these black hole pairs we've been missing."
Previous observations in X-rays and at other wavelengths indicated that a single supermassive black hole existed in the center of NGC 3393. However, a long look by Chandra allowed the researchers to detect and separate the dual black holes. Both black holes are actively growing and emitting X-rays as gas falls towards them and becomes hotter.
When two equal-sized spiral galaxies merge, astronomers think it should result in the formation of a black hole pair and a galaxy with a disrupted appearance and intense star formation. A well-known example is the pair of supermassive black holes in NGC 6240, which is located about 330 million light years from Earth.
However, NGC 3393 is a well-organized spiral galaxy, and its central bulge is dominated by old stars. These are unusual properties for a galaxy containing a pair of black holes. Instead, NGC 3393 may be the first known instance where the merger of a large galaxy and a much smaller one, dubbed a "minor merger" by scientists, has resulted in the formation of a pair of supermassive black holes. In fact, some theories say that minor mergers should be the most common way for black hole pairs to form, but good candidates have been difficult to find because the merged galaxy is expected to look so typical.
"The two galaxies have merged without a trace of the earlier collision, apart from the two black holes," said co-author Junfeng Wang, also from CfA. "If there was a mismatch in size between the two galaxies it wouldn't be a surprise for the bigger one to survive unscathed."
If this was a minor merger, the black hole in the smaller galaxy should have had a smaller mass than the other black hole before their host galaxies started to collide. Good estimates of the masses of both black holes are not yet available to test this idea, although the observations do show that both black holes are more massive than about a million suns. Assuming a minor merger occurred, the black holes should eventually merge after about a billion years.
Both of the supermassive black holes are heavily obscured by dust and gas, which makes them difficult to observe in optical light. Because X-rays are more energetic, they can penetrate this obscuring material. Chandra's X-ray spectra show clear signatures of a pair of supermassive black holes.
The NGC 3393 discovery has some similarities to a possible pair of supermassive black holes found recently by Julia Comerford of the University of Texas at Austin, also using Chandra data. Two X-ray sources, which may be due to supermassive black holes in a galaxy about two billion light years from Earth, are separated by about 6,500 light years. As in NGC 3393, the host galaxy shows no signs of disturbance or extreme amounts of star formation. However, no structure of any sort, including spiral features, is seen in the galaxy. Also, one of the sources could be explained by a jet, implying only one supermassive black hole is located in the galaxy.
"Collisions and mergers are one of the most important ways for galaxies and black holes to grow," said co-author Guido Risaliti of CfA and the National Institute for Astrophysics in Florence, Italy. "Finding a black hole pair in a spiral galaxy is an important clue in our quest to learn how this happens."
NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.
08/09/2011 - Probe Pictures Moon Landing Sites
Remarkable new images of the Apollo landing sites on the Moon have been released by Nasa.
The pictures clearly show the hardware left on the lunar surface by American astronauts in the 1960s and 70s, including Apollo 17's "Moon buggy".
The images were acquired by the robotic Lunar Reconnaissance Orbiter (LRO), which has been circling Earth's satellite since 2009.
Such shots have been returned before, but these are the best yet.
LRO has recently lowered its orbit from 50km above the Moon's surface to just 25km.
This makes it easier to see equipment, such as the descent stages that put the astronauts on the surface. Some of the science experiments are visible, also - as are the trails of bootmarks left in the dirt as the crews positioned these science packages.
Harrison Schmitt sits in the LRVThe Apollo 17, 14 and 12 sites are the focus of the latest release.
They were viewed by the narrow-angle imaging system on LRO's Lunar Reconnaissance Orbiter Camera (LROC) instrument.
At the lower altitude, this instrument sees objects at a resolution of 25cm by 25cm per pixel.
In an extreme blow-up of the Apollo 17 Lunar Roving Vehicle (LRV), it is just possible to discern the condition in which the astronauts Eugene Cernan and Harrison Schmitt parked the buggy - with its wheels turned to the left.
LRO has been a highly productive mission. It has now returned several hundred thousands pictures of the lunar surface.
The probe was originally conceived as a robotic precursor to future manned missions. However, when Nasa might return to the lunar body with astronauts is not clear. Last year, US politicians cancelled the project, known as Constellation, that was intended to achieve this feat.
"We all like to obsess and look at the Apollo landing site images because it's fun," said Mark Robinson, the LROC principal investigator from Arizona State University, Tempe.
"People actually used to be able to go to the Moon; people used to explore the Moon - and hopefully sometime in the future that will continue again. But LROC is looking at the whole Moon and we've taken about 1,500 of these high-resolution images distributed all around the Moon… and this is just a huge resource for anybody studying the Moon, doing science; and engineers planning to go back to the Moon in general and to specific sites."
Erosion processes on the Moon work much slower than on an active planet like Earth. Eventually, though, all traces of the Moon landings will be erased.
The lunar body is constantly bombarded by micrometeorites that will, in time, mix up the boottracks and break down the equipment. It has been estimated that rock at the surface erodes at a rate of about 1mm per million years.
"In human years, it may seem like forever, but in geologic terms probably there will be no traces of the Apollo exploration in let's say 10 to 100 million years," said Dr Robinson.
On Thursday, Nasa will launch its latest Moon mission - the Gravity Recovery and Interior Laboratory (Grail).
This is a pair of satellites that will survey the Moon's gravity in unprecedented detail. The data will reveal its internal structure, helping to explain how the lunar body formed and why its nearside now looks so different from its farside.
23/08/2011 - Colliding solar systems spell disaster for habitable planets
Computer simulations have revealed the reason why some exoplanets are inclined at large angles and why this might lead to habitable planets being evicted from planetary systems.
Planets are thought to form within giant discs of gas and dust which surround young protostars. Clumps of material start to stick together and eventually collide with each other to create a protoplanet, which then sweeps up even more material from the disc. This protoplanetary disc rotates in the same direction as the protostar and should result in planets orbiting in the same plane as the equator of the star. However, there are many exoplanets which have broken the rules and orbit at large angles from the equatorial plane. What makes these systems so different?
A team of German and British astronomers have been running computer simulations in order to solve this mystery. They have discovered that if a protoplanetary disc, which they dub the “bullet”, collides with another disc known as the “target” then the bullet disc will steal material from the target disc. This extra gas and dust will result in the bullet disc moving from the equatorial plane of the star to a plane which is at a large angle from the stars equator. The chance of such collisions between discs rises if the discs exist within a star cluster. “Encounters between stars and/or protostellar objects are expected to be highly likely or even unavoidable in dense clusters like the Trapezium Cluster in the Orion Nebula,” Ingo Thies from the University of Bonn tellsAstronomy Now. “However, other kinds of ‘target clouds’ than a huge disc are possible, like dense filaments, clumps etc. This makes encounters even more likely.”
The exoplanets that have been discovered so far exhibit other unusual properties, such as orbiting very close to their parent star or orbiting in highly elliptical orbits. “However, while the first two can indeed be explained by unstable planetary systems, e.g with too small radial separations between the orbits, or with one or two very massive planets, the strongly inclined orbits require an initial misalignment in such a system,” explains Thies.
The extra material in the disc not only results in inclined planets, but it can go so far as to cause the protoplanetary disc to rotate in the opposite direction to the star. This results in planets which orbit in the opposite direction to which the star is spinning, known as retrograde motion. If it turns out that some of these highly inclined planets do not orbit in the same plane as each other, then the system can be come very unstable. The increased likelihood of these inclined planets in star clusters implies that the number of habitable terrestrial planets is probably less than currently expected, because unstable systems will eject smaller planets.
“Unstable and thus uninhabitable planetary systems may also result from unusually dense circumstellar discs, since more massive giant planets may form and perturb the orbits of other planets,” adds Thies. However, this bleak outcome will not always be the case. “If the initial disc and the ring of new material have enough time to align, and no planets have yet formed therein, there will probably only be a moderate mutual tilt (a few degrees, like the 2-3 degrees mutual inclination of the planets in the Solar System).”
Thies remarks that the planetary systems discovered to date are unlike our own Solar System as they orbit much closer to their parent stars. “Future detections of transiting planets on wider orbits will hopefully help to answer the question whether misaligned orbits are similarly common in Solar-like planetary systems.”
23/08/2011 - The Moon gets a face-lift
New analysis of lunar rocks suggests that Earth's Moon could be around 200 million years younger than previously thought.
The leading theory of our Moon's formation is that it was born from a giant impact between a Mars-sized body and the early Earth; the debris from this cataclysmic collision coalesced to form the Moon. As the Moon cooled it solidified into different mineral components, from which relative ages can be deduced.
In the giant impact model, a rock type called ferroan anorthosite (FAN) represents the oldest suite of crustal rocks, but accurately dating its age by analysing the isotopes of the radioactive elements lead and neodymium has been hampered by the very low concentrations of the elements used in the technique, and the fact that most old rocks of the lunar crust have been affected by later impacts. Furthermore, FAN is predominantly made of one mineral, plagioclase feldspar, but most applicable dating methods require at least two compositionally distinct minerals.
"We were lucky in finding a piece of sample 60025 that had an unusually large amount of the mineral pyroxene in addition to plagioclase," Richard Carlson of the Carnegie Institution for Science in Washington tells Astronomy Now. "We used conventional techniques that have been gradually improved over the 40 years since the lunar landings to improve on previous dating attempts and we worked on a split of the sample that was mineralogically amenable to this study."
The refined analysis places the FAN's age at 4.36 billion years, significantly younger than the oldest estimated age of 4.568 billion years, equivalent to the age of the Solar System. The new, young age correlates with some of Earth's oldest minerals, suggesting that the oldest crusts on both Earth and Moon formed at approximately the same time, and that this time dates from shortly after the giant impact.
"Thermal models show that a molten Moon would crystallize to the point of forming a crust similar in composition to the rock we dated within a few hundred to a few thousand years," says Carlson. "If the Moon's crust did not form in this manner, then it is possible to likely that the age of this rock does not correspond to the age of the Moon."
The findings imply that either the Moon solidified a lot later than previous estimates, that the theory of lunar crust formation by a solidifying magma ocean is incorrect, or that the rocks studied do not represent the oldest type of lunar sample.
Carlson is confident that the team's findings strengthen the idea of a giant impact theory for the Moon's formation, however. "Theoretical models of planet accumulation allow a few moderately large planetesimals to survive for long times (100's of million years), so a "late" giant impact is somewhat expected in part because the consequences of earlier big impacts will be overprinted by the last big impact. There is no other obvious mechanism to form a Moon this young."
The research team was led by Lars E. Borg of the Lawrence Livermore National Laboratory and the work is published in the 18 August issue of the journal Nature.
23/08/2011 - New rover snapshots capture Endeavour Crater vistas
NASA's Mars Exploration Rover Opportunity has captured new images of intriguing martian terrain from a small crater near the rim of the large Endeavour Crater. The rover arrived at the 13-mile-diameter (21 kilometers) Endeavour on August 9 after a journey of almost 3 years.
Opportunity is now examining the ejected material from the small crater named Odyssey. The rover is approaching a large block of ejecta for investigation with tools on the rover's robotic arm.
Opportunity and Spirit completed their 3-month primary missions on Mars in April 2004. Both rovers continued for years of bonus, extended missions. Both have made important discoveries about wet environments on ancient Mars that may have been favorable for supporting microbial life. Spirit ended communications in March 2010.
23/08/2011 - Astronomers find ice and possibly methane on Snow White, a distant dwarf planet
Astronomers at the California Institute of Technology (Caltech) have discovered that the dwarf planet 2007 OR10 (Snow White) is an icy world, with about half its surface covered in water ice that once flowed from ancient, slush-spewing volcanoes. The new findings also suggest that the red-tinged dwarf planet may be covered in a thin layer of methane, the remnants of an atmosphere that’s slowly being lost into space.
“You get to see this nice picture of what once was an active little world with water volcanoes and an atmosphere, and it’s now just frozen, dead, with an atmosphere that’s slowly slipping away,” said Mike Brown from Caltech.
Snow White, which was discovered in 2007 by Meg Schwamb from Caltech, orbits the Sun at the edge of the solar system and is about half the size of Pluto, making it the fifth-largest dwarf planet. At the time, Brown had guessed incorrectly that it was an icy body that had broken off from another dwarf planet named Haumea; he nicknamed it Snow White for its presumed white color.
Soon, however, follow-up observations revealed that Snow White is actually one of the reddest objects in the solar system. A few other dwarf planets at the edge of the solar system are also red. These distant dwarf planets are themselves part of a larger group of icy bodies called Kuiper Belt Objects (KBOs). As far as the researchers could tell, Snow White, though relatively large, was unremarkable — just one out of more than 400 potential dwarf planets that are among hundreds of thousands of KBOs.
“With all of the dwarf planets that are this big, there’s something interesting about them; they always tell us something,” Brown said. “This one frustrated us for years because we didn’t know what it was telling us.” At that time, the Near Infrared Camera (NIRC) at the Keck Observatory was the best instrument astronomers had to study KBOs, said Brown. But NIRC had just been retired, so no one could observe 2007 OR10 in detail. “It kind of languished,” he said.
Meanwhile, Adam Burgasser from the University of California, San Diego, was helping design a new instrument called the Folded-port Infrared Echellette (FIRE). Last fall, Brown, Burgasser, and Wesley Fraser from Caltech used this instrument with the 6.5-meter Magellan Baade Telescope in Chile to take a closer look at 2007 OR10.
As expected, Snow White was red. But to their surprise, the spectrum revealed that the surface was covered in water ice. “That was a big shock,” Brown said. “Water ice is not red.” Although ice is common in the outer solar system, it’s almost always white.
There is, however, one other dwarf planet that’s both red and covered with water ice: Quaoar, which Brown helped discover in 2002. Slightly smaller than Snow White, Quaoar is still big enough to have had an atmosphere and a surface covered with volcanoes that spewed an icy slush, which then froze solid as it flowed over the surface.
But because Quaoar isn’t as big as dwarf planets like Pluto or Eris, it could not hold onto volatile compounds like methane, carbon monoxide, or nitrogen as long. A couple of billion years after Quaoar formed, it began to lose its atmosphere to space; now, all that remains is some methane. Over time, exposure to the radiation from space turned that methane, which consists of a carbon atom bonded to four hydrogen atoms, into long hydrocarbon chains that look red. Like the frost that covers a lawn on a cold morning, the irradiated methane sits on Quaoar’s icy surface, giving it a rosy hue.
The spectrum of 2007 OR10 looks similar to Quaoar’s, suggesting that what happened on Quaoar also happened on 2007 OR10. “That combination — red and water — says to me, ‘methane,’” Brown said. “We’re basically looking at the last gasp of Snow White. For 4.5 billion years, Snow White has been sitting out there, slowly losing its atmosphere, and now there’s just a little bit left.”
Although Snow White’s spectrum clearly shows the presence of water ice, Brown said, the evidence for methane is not yet definitive. To find out, the astronomers will have to use a big telescope like the one at the Keck Observatory. If it turns out that Snow White does have methane, it will join Quaoar as one of only two dwarf planets that straddle the border between the handful of objects large enough to hold onto volatile compounds and the smaller bodies that make up the vast majority of KBOs.
Another task, Brown said, is to give the dwarf planet an official name, since Snow White was just a nickname he and his colleagues used. Besides, the moniker no longer makes sense for describing this red object. Before the discovery of water ice and the possibility of methane, “2007 OR10” might have sufficed for the astronomy community because it didn’t seem noteworthy enough to warrant an official name. “We didn’t know Snow White was interesting,” Brown said. “Now we know it’s worth studying.”
31/07/2011 - Trojan asteroid seen in Earth's orbit by Wise telescope
Astronomers have detected an asteroid not far from Earth, moving in the same orbit around the Sun.
The 200-300m-wide rock sits in front of our planet at a gravitational "sweet spot", and poses no danger.
Its position in the sky makes it a so-called Trojan asteroid - a type previously detected only at Jupiter, Neptune and Mars.
2010 TK7, as it is known, was found by Nasa's Wise telescope. The discovery is reported in this week's Nature journal.
It is a fascinating observation because the relative stability and proximity of Trojans would make possible targets for astronaut missions when we eventually go beyond the space station.
2010 TK7 is probably not the rock of choice, simply because it travels too far above and below the plane of Earth's orbit, which would require a lot of fuel to reach it.
Nonetheless, its detection means it is highly likely there are other, more suitable Trojans out there waiting to be found.
The difficulty is the viewing geometry that puts any Trojan, from the perspective of an Earth-based telescope, in bright skies.
It took an orbiting telescope sensitive to infrared light to pick up 2010 TK7.
Wise, the Wide-field Infrared Survey Explorer launched in 2009, examined more than 500 Near-Earth Objects (NEOs), 123 of which were new to science.
The authors of the Nature paper sifted through data on these rocks, looking for the candidates that might be Trojans.
Follow-up work on the Canada-France-Hawaii Telescope confirmed the status of 2010 TK7.
It traces quite a complex path at its orbital point. Currently, it is about 80 million km from Earth, and should come no closer than about 25 million km.
The team says its orbit appears stable at least for the next 10,000 years.
2010 TK7's existence should not really be a surprise. Jupiter, Neptune and Mars all have collections of rocks sitting in the so-called Lagrange points 60 degrees ahead of or behind the planets in their orbits.
In the case of Jupiter, the number of Trojans now tops 1,000 rocks.
"These objects are difficult to find from Earth, simply because they're not very big and they're pretty faint, and they're close to the Sun as seen from Earth," explained Christian Veillet from the Canada-France-Hawaii Telescope and a co-author on the Nature study.
"But we can find them from space, and future satellites will likely find some more. We think that there are others which will be very close to the Earth and have motions that make them relatively easy to reach. So, they could be potential targets to go to with spacecraft," he told BBC News.
31/07/2011 - Black hole hosts largest, oldest water reservoir
A water cloud containing the equivalent of 140 trillion times the water held in Earth's oceans has been detected around a quasar powered by a giant black hole 12 billion light years away.
Although water is expected even earlier in the Universe's existence, the discovery pushes the detection of water one billion years closer to the start of the Universe than any previous find. “It’s another demonstration that water is pervasive throughout the Universe, even at the very earliest times,” says Matt Bradford, lead author of the paper describing the results that will appear in Astrophysical Journal Letters.
The quasar, APM 08279+5255, is powered by a black hole 20 billion times more massive than our Sun and was scrutinized by the Z-Spec instrument at the ten-metre Caltech Submillimeter Observatory in Hawaii, which revealed the spectral fingerprint of water. Confirmation came from the Combined Array for Research in Millimeter-Wave Astronomy (CARMA), a linked array of 15 radio telescope dishes in California.
The water-rich cloud spans hundreds of light years around the black hole, boasting 4,000 times more water vapor than our own Milky Way – most of our Galaxy's water is frozen. The most surprising aspect of the discovery was that the vapor is five times hotter and 10-100 times denser than that observed in galaxies like the Milky Way. X-ray and infrared radiation pour out from the quasar, and may provide the explanation.
“We know that water molecules are formed in regions that are hot and dense,” explains co-author Alberto Bolatto of the University of Maryland. “In a colder environment a lot of the water vapor would stick to interstellar dust grains, coating them with a film of ice. Here, that is not possible because the dust grains themselves are hot, and in fact any ice-coated grain brought to the vicinity of the quasar would have its mantle evaporated, so that may help explain the unusual abundance of water around APM 08279 too. Finally, exciting water vapor molecules to the point that they emit in the lines we observe also requires a high radiation field (or a high temperature and density), so the radiation field not only helps the chemistry that makes water, but it also helps in making it emit at the wavelengths we observe.”
As to the fate of the vapor cloud, some material may clump and condense into stars or alternatively be ejected by the quasar, while some might fall into and feed the black hole – estimates based on the quantity of material observed suggest that it could grow up to six times its present size.
31/07/2011 - Dying star’s last gasps provides new Kepler target
A new planetary nebula, recently discovered thanks to the combined efforts of amateur and professional astronomers and within sight of the Kepler spacecraft, could hold the key to understanding how our own Sun's life will end.
The detection of the nebula, Kronberger 61 (Kn 61), along with a striking new image of it from the Gemini Observatory, was presented this week at the International Astronomical Union symposium in Tenerife. It's named after its discoverer, Matthias Kronberger, a member of a group of amateur astronomers called the Deep Sky Hunters, who devote their spare time to hunting through existing datasets to find objects like this. Such a search is difficult because they are "extremely rare and each, a valuable gem," according to George Jacoby of the Giant Magellan Telescope Organization and the Carnegie Observatories.
Planetary nebulae are giant shells of ionised glowing gas shed from the outer layers of geriatric stars. Their misleading name is a relic of their original 18th Century observers, and their small telescopes, who mistakenly thought they were similar to the gas giant planets in our own Solar System. Over 3,000 have been identified, making them common throughout our galactic neighborhood, but questions remain about their formation.
"Explaining the puffs left behind when medium sized stars...expel their last breaths is a source of heated debate among astronomers, especially the part that companions might play," says team-member Orsola De Marco of Sydney's Macquarie University. "Some recent theories suggest that planetary nebulae form only in close binary or even planetary systems — on the other hand, the conventional textbook explanation is that most stars, even solo stars like our Sun, will meet this fate. That might just be too simple."
Currently companions have only been found around a low percentage of the central stars associated with planetary nebulae. However, as Jacoby points out, "this is quite likely due to our inability to detect these binaries from the ground." This situation will soon improve thanks to the sensitivity of NASA's Kepler planet-finding mission. It currently monitors more than 150,000 stars within the constellation of Cygnus, looking for the small fluctuations in brightness which indicate the presence of a companion, planetary or otherwise.
To increase the odds of finding good planetary nebula candidates to add to Kepler's monitoring list, professional astronomers enlisted the help of the Deep Sky Hunters. Kn 61 is their second confirmed detection to date, with a possible third to come. As Kronberger comments “…the field where Kepler points to is very scarce in PNe (planetary nebulae) so Dr. Jacoby approached me at the beginning of this year and asked me if I could do a quick survey of the Kepler field for any overlooked planetaries in order to improve statistics. Which I did - and only a few hours of surveying I came across a very faint, bluish shell with a very pronounced blue central star that perfectly fit into this category. And yes – the image tells the rest of the story!”
Jacoby adds: "Without this close collaboration with amateurs, this discovery would probably not have been made before the end of the Kepler mission. Professionals, using precious telescope time, aren't as flexible as amateurs who did this using existing data and in their spare time. This was a fantastic pro-am collaboration of discovery".
31/07/2011 - Blasted alien worlds put on a dazzling show
Scientists at the Harvard-Smithsonian Center for Astrophysics have looked into what would happen if an alien gas giant, which tightly orbits its star at just a few million miles, were struck by a stellar eruption.
Ofer Cohen, a postdoctoral fellow at Harvard, and his colleagues used computer models to uncover what effects a stellar blast would have on an exoplanet's atmosphere and surrounding magnetosphere. The new research illustrates that aurorae on distant hot jupiters can be up to 100–1000 times more energetic than the aurorae we see on Earth.
Aurorae can be seen on the Earth as the Northern and Southern Lights, and can observed at the polar regions of our planet. The curtains of green and red are created when energetic particles from the Sun slam into our planet's magnetic field. “The topology of the aurora is determined by the location of the 'open' magnetic field lines, where particles along these lines can penetrate and hit the planetary atmosphere,” says Cohen, who is lead author of the research paper accepted for publication in The Astrophysical Journal . “There particles hit the atmospheric neutral atoms so that photons are emitted via the interaction to generate the light that we see.” It is this process that can occur on distant worlds as they dance around their parent stars. “The exact location of the auroral region depends on how strong the coronal mass ejection driver is,” he adds. “The stronger it is, the lower the latitude the aurora will be.”
A coronal mass ejection, or CME, is a gigantic blast from the Sun which throws billions of tons of electrically charged hot gas into our Solar System – on some occasions we have been on the receiving end of the Sun's fiery temper. A CME can disrupt the Earth's protective magnetic shield – the magnetosphere – causing a geomagnetic storm. “During the Halloween storm event in 2003, the aurora could be seen in Florida and Texas due to its massive strength,” says Cohen. Two other famous solar storms are the 13 March 1989 event when one a storm knocked out power across the entire Canadian province of Quebec for more than nine hours, and the Carrington Event of 1859, whose severity is the greatest to date, shocking telegraph operators and setting some areas on fire.
In the case of an alien gas giant close to its star, it would be subject to these extreme forces creating much stronger and more focused blasts in comparison to our Solar System, where the CME spreads out as it travels through space, somewhat softening the blow. “The main difference is that in our Solar System and on Earth, the CME is not affected by the planet, since it is much larger,” says Cohen. “Think about a large wave in the sea that hits a small stone. The stone is affected by the wave, but the wave does not 'feel' the stone. Now think about a very large stone, an island; in this case, the wave will break as it hits the island. This is what happens in our simulation – the CME and the planet are comparable in size, so that the CME is highly affected by the interaction.”
In their simulation, a CME blasts the hot jupiter, with a strength analagous to being within a mile of an active volcano, weakening its magnetic shield. The CME particles then reach the the gas giant’s atmosphere, creating a display of auroral lights around the equator. Over the course of 6 hours, the aurora ripples up and down towards the planet's north and south poles before gradually fading away. “In the simulation, the aurora starts near the equator and migrates towards higher latitudes,” says Cohen. “This is due to the fact that the CME opens up some of the originally closed field lines of the planet near the equator. The main point here is that the aurora on such a planet is not only much more intense, but it is also all over the place.”
However, despite the extremity of the forces involved, the exoplanet's magnetic field shield still manages to protect its atmosphere from erosion. “Our calculations show how well the protective mechanism works,” explains Cohen. “Even a planet with a magnetic field much weaker than Jupiter's would stay relatively safe.”
The investigation is also important in our understanding of potentially habitable rocky worlds orbiting distant stars. However, since there are more red dwarf stars in our Galaxy, scientists have suggested that we should be focussing on them in our search for Earth-like planets, rather than hotter Sun-like stars. Since red dwarfs are cooler, a planet must orbit very closely to be warm enough to accommodate liquid water and it is at this distance that it would be subject to violent stellar eruptions.
“In this simulation, the detailed physics of the planetary upper atmosphere and the magnetosphere could not be studied in detail, due to the computational limitations,” says Cohen of his research. “We plan to extend our study to models for the upper atmosphere of the planet, so that the detailed impact, as well as the parametric study, could be done in a more precise manner.”
31/07/2011 - Enceladus feeds water to Saturn
A 14 year old mystery has been solved as astronomers discover that plumes of water gushing from Saturn’s moon Enceladus are the source of water in the planet's upper atmosphere.
Water vapour was detected in a massive torus surrounding Saturn by astronomers using ESA's Herschel Space Observatory. The torus has a thickness equivalent to Saturn's radius and it extends to a distance ten times wider. The torus remained invisible up until now as water vapour is translucent in visible light at such distances, however, infrared observations by Herschel easily revealed Saturn's secret water stash, which then rains down into the ringed planet's upper atmosphere.
Jets of water vapour spewing from the south pole of Saturn's moon Enceladus at rates of around 250 kilograms every second are what feed this torus. The jets were first observed by the Cassini space probe in 2006, and originate from a region of winding fissures dubbed the Tiger Stripes.
Water vapour was first discovered in Saturn’s upper atmosphere in 1997 using ESA’s Infrared Space Observatory, but until now astronomers have been baffled by how it got there. While water can exist in the lower atmosphere, the vapour pressure is too low higher in the atmosphere for it to occur naturally.
“We have a similar situation on the Earth,” explains Paul Hartogh of the Max-Planck-Institut für Sonnensystemforschung and lead author of the Astronomy & Astrophysics paper. “The relative abundance of water in air on the ground can be as high as four percent. With increasing altitude the temperature in the atmosphere is decreasing and in the tropopause region (10-18 kilometres high) it reaches a relative minimum, as low as 190 Kelvin. The vapour pressure of water decreases dramatically at 190 Kelvin so that only about four parts per million of water vapour contributes to air. This is 10,000 times less than on the ground.”
However there is even less water vapour on Saturn due to even lower temperatures in the gas giant’s tropopause. “On Saturn the tropopause temperature is around 85 - 90 Kelvin,” says Hartogh. “At these low temperatures the vapour pressure of water is even more than a billion times lower than in the Earth tropopause. Water vapour cannot exist there and therefore cannot be transported into Saturn's stratosphere from below.”
This means that water vapour cannot exist on Saturn unless it comes from an external source. The amount of water detected in Saturn’s atmosphere by Herschel is equivalent to the amount that is being rained down on the planet from the surrounding torus. Enceladus is now unique as this precipitation makes it the only moon in the Solar System to affect its planet's composition.
31/07/2011 - Curiosity rover will explore 'scenic' Gale crater on Mars
The next Mars rover will make a pinpoint landing inside Gale crater, a scenic impact site adorned with ragged rock formations and a colossal mountain rising more than 15,000 feet high, NASA announced Friday.
Scientists will dispatch the $2.5 billion Curiosity rover to Mars as early as Nov. 25. The robot is outfitted with 17 cameras and nearly a dozen instruments to determine whether Mars was ever habitable for life.
After considering 60 landing site candidates, scientists recommended Gale crater as Curiosity's destination because it offered the widest array of geologic research opportunities, giving the rover a window into a large period of Martian history.
If it launches on time, Curiosity will arrive at Mars on Aug. 6, 2012.
Michael Meyer, the lead researcher for NASA's Mars program, said there was a "slight preference" for Gale among the four landing site finalists. It was likely once home to a deep lake.
"There was a preference for Gale in that it's not a one-trick pony," Meyer said. "There are several different environmental settings that can be explored, any one of which might have the possibility of [holding] organic compounds."
"In the end, we picked the one that felt best," said John Grotzinger, the Mars Science Laboratory mission's chief scientist at the Jet Propulsion Laboratory in Pasadena, Calif.
Geologists do not expect Curiosity to find a fossil on Mars, but it could uncover the chemical fingerprint of past life amid organic compounds.
If Curiosity can find elusive carbon-based organic material inside Gale's rocks, scientists will obtain evidence that the ingredients for life were once plentiful on Mars.
Previous NASA missions already confirmed water was once common on the surface of Mars. After retreating during a period of climate change, the water is now held in ice caps at the Martian poles and embedded inside mineral compounds in some soils.
The exploration of the scenic 96-mile-wide crater will also return thousands of images from Curiosity's cameras.
"It's also going to be an incredibly beautiful place," said Dawn Sumner, a geologist at the University of California, Davis. "It will be a lot like areas in the Southwest [United States], places like Monument Valley where we'll have these big cliffs with the rover going between them."
Positioned just south of the Martian equator, the crater's central peak is taller than any mountain in the continental United States.
After touching down on relatively flat terrain a few miles from the base of the mound, Curiosity will drive south toward the peak and begin to climb thousands of feet up its flank, pausing to examine clay and sulfate salt minerals along the way, Grotzinger said.
Dried-up stream channels along the edge of the mound will allow access up the mountain.
Curiosity's mission is supposed to last two years after landing, but scientists are hopeful the rover will continue the climb up Gale's lofty mountain for years more. Scientists say the most attractive scientific targets are near the base of the central mountain, ensuring the rover will produce quality results early in the mission.
As the rover ascends the mountain, it will encounter rocks and soil left behind as waters receded when Mars transitioned from a warm, wet planet into the cold and desolate world known today.
Curiosity's analysis of clays and sulfates will tell scientists how much water was once present at Gale, the characteristics of the water and how it evaporated, according to Sumner.
"What we've learned is if you start at the bottom of the layers and you work your way to the top, it's like reading a novel," Grotzinger said. "And we think Gale is going to be a great novel."
Using high-resolution imagery from a sharp-eyed camera on NASA's Mars Reconnaissance Orbiter, the landing site selection committee mapped hazards and plotted driving paths for the rover at each of the four finalist locations.
Spectrometers on orbiting satellites at Mars indicated Gale had the widest variety of environments of all the sites, harboring both relatively fresh and ancient material inside the crater, which scientists believe is about 3 billion years old.
Curiosity is NASA's first mobile Mars surface station since the Spirit and Opportunity rovers arrived at the Red Planet in 2004.
The rover is five times as massive as the previous generation of Mars robots, and its scientific gear is 10 times heavier.
After braving the hot temperatures of entry into the Martian atmosphere in a blunt heat shield, Curiosity will descend to a hover with a rocket-powered descent stage. A state-of-the-art "sky crane" will lower the nearly 2,000-pound rover on a bridle to the surface directly on its wheels.
The futuristic descent and landing system replaces air bags, a tried-and-true but rudimentary touchdown technique. With the new system, engineers expect to guide Curiosity to a precise landing inside a narrow error corridor.
"We've done our homework," Meyer said. "The engineers have designed a spacecraft to get us to where we want to go."
The rover's mobility system has the ability to climb a 20-degree incline. It's designed to drive at least 12 miles, according to Michael Watkins, an MSL project engineer at JPL.
"Geologists like climbing up cliffs, and we get to go to those places with this rover for the first time on Mars," Sumner said.
22/07/2011 - Are elliptical galaxies much younger than previously thought?
The standard model for elliptical galaxy formation is challenged by a new result uncovered by an international team of astronomers from the Atlas3D collaboration. The first results from the group’s study on two elliptical galaxies exhibiting features characteristic of a fairly recent merger, suggest they are 5 times younger than commonly thought.
The accepted belief on the mass assembly history of massive elliptical galaxies based on their stellar population leads to an age between 7 and 10 billion years old. A different story is shaping up based on ultra-deep images of two galaxies observed with the MegaCam camera mounted on the Canada-France-Hawaii Telescope (CFHT).
The astronomers established that the formation of the two elliptical galaxies, NGC 680 and NGC 5557, originated from a merger of two giant spiral galaxies that took place only 1 to 3 billion years ago. The age estimate is based on the presence of ultra-faint filaments in the distant outskirts of the galaxies. These features called tidal streams are typical residuals from a galaxy merger. They are known not to survive in this shape and brightness for more than a few billion years, hence the new age estimate of the resulting elliptical galaxies. These structures were detected for the first time thanks to an imaging technique boosting the capabilities of CFHT's wide-field optical imager MegaCam.
The Atlas3D team conducts a systematic survey of more than 100 nearby elliptical galaxies. If the current result based on the first two galaxies is confirmed on the larger sample, i.e. if faint extended features are frequently detected, the standard model for elliptical galaxies formation should be revisited.
22/07/2011 - Exoplanet aurora: An out-of-this-world sight
Earth's aurorae, or northern and southern lights, provide a dazzling light show to people living in the polar regions. Shimmering curtains of green and red undulate across the sky like a living thing. New research shows that aurorae on distant "hot Jupiters" could be 100 to 1,000 times brighter than earthly aurorae. They also would ripple from equator to poles, due to the planet's proximity to any stellar eruptions, treating the entire planet to an otherworldly spectacle.
"I'd love to get a reservation on a tour to see these aurorae!" said Ofer Cohen from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts.
Earth's aurorae are created when energetic particles from the Sun slam into our planet's magnetic field. The field guides solar particles toward the poles, where they smash into Earth's atmosphere, causing air molecules to glow like a neon sign. The same process can occur on planets orbiting distant stars, known as exoplanets.
Particularly strong aurorae result when Earth is hit by a coronal mass ejection (CME) — a gigantic blast that sends billions of tons of solar plasma (electrically charged hot gas) into the solar system. A CME can disrupt Earth's magnetosphere — the bubble of space protected by Earth's magnetic field — causing a geomagnetic storm. In 1989, a CME hit Earth with such force that the resulting geomagnetic storm blacked out huge regions of Quebec, Canada.
Cohen and his colleagues used computer models to study what would happen if a gas giant in a close orbit, just a few million miles from its star, were hit by a stellar eruption. He wanted to learn the effect on the exoplanet's atmosphere and surrounding magnetosphere.
The alien gas giant would be subjected to extreme forces. In our solar system, a CME spreads out as it travels through space, so it's more diffuse once it reaches us. A hot Jupiter would feel a stronger and more focused blast, like the difference between being 100 miles (160 kilometers) from an erupting volcano or 1 mile (1.6 km) away.
"The impact to the exoplanet would be completely different than what we see in our solar system and much more violent," said Vinay Kashyap from CfA.
In the model, a CME hits the hot Jupiter and weakens its magnetic shield, and then CME particles reach the gas giant's atmosphere. Its aurora lights up in a ring around the equator 100 to 1,000 times more energetic than earthly aurorae. Over the course of about 6 hours, the aurora then ripples up and down toward the planet's north and south poles before gradually fading away.
Despite the extreme forces involved, the exoplanet's magnetic field shields its atmosphere from erosion.
"Our calculations show how well the planet's protective mechanism works," said Cohen. "Even a planet with a magnetic field much weaker than Jupiter's would stay relatively safe."
This work has important implications for the habitability of rocky worlds orbiting distant stars. Because red dwarf stars are the most common stars in our galaxy, astronomers have suggested focusing on them in the search for earthlike worlds.
However, since a red dwarf is cooler than our Sun, a rocky planet would have to orbit very close to the star to be warm enough for liquid water. There, it would be subjected to the sort of violent stellar eruptions Cohen and his colleagues studied. Their future work will examine whether rocky worlds could shield themselves from such eruptions
22/07/2011 - Mars rover aims for deep crater
Nasa's next Mars rover will be aimed at one of the planet's deepest craters.
MSL-Curiosity weighs almost a tonne and is the size of a Mini Cooper.
It will carry instruments to study whether Mars had the conditions in the past to support microbial life.
The US space agency has selected an equatorial depression called Gale Crater to investigate that question.
The $2.5bn rover will launch from Florida in November.
It should touch-down at the Red planet in August 2012.
Gale Crater is about 155km in diameter, and its lowest point is about 4.6km below datum, the reference point on Mars from which all other elevations are measured.
The landing zone will be much narrower than the crater's width. But Nasa has high confidence the rocket-powered descent system designed for MSL-Curiosity can put it inside a target zone less than 20km across.
If this Skycrane, as it is known, works as planned, the rover will be delivered close to the central peak of the crater.
This is a huge mountain that contains layers of deposits that should offer an impressive view of millions of years of Martian geological history."What we've learnt over 150 years of exploration is that if you start at the bottom of the pile of layers and you go to the top, it's like reading a novel," said mission project scientist John Grotzinger from Nasa's Jet Propulsion Laboratory.
"We think Gale Crater is going to be a great novel about the early environmental evolution of Mars that offers strong prospects potentially for the discovery of habitable environments, and maybe even a shot at discovering organic compounds."
Dr Grotzinger stressed that MSL-Curiosity is not a life-detection mission; it cannot identify microbes or even microbial fossils. But it can assess whether ancient conditions could have supported organisms.
This means Gale must show evidence for the past presence of water, a source of energy with which life forms could have metabolised, and a source of organic compounds with which organisms could have built their structures.
Gale has been chosen because satellite imagery suggests it may well be one of the best places on Mars to look for these biological preconditions.
The Skycrane will lower MSL-Curiosity on to the relatively flat valley floor on the end of tethers before blasting away to a safe distance. The robot will then drive up to the base of the central mountain.
In front of it, the rover should should find abundant quantities of clay minerals that will give fresh insight into the very wet early epoch of the Red Planet. Above the clays, the deposits change to sulphates, which relate to a period in time when Mars was still wet but was beginning to dry out.
In addition, there is evidence water flowed down the mountain at some point in the past, cutting a deep gully and depositing sediments out on the plain.
The rover will get to investigate all of this.
"The suite of things that we can see at Gale represents a diverse number of environments over a long period of time, possibly tens to hundreds of millions of years, plus the modern environment," said Dawn Sumner, a geologist at the University of California Davis, US.
"It's also going to be just an incredibly beautiful place - it will be a lot like the southwest of the US, areas like Monument Valley where you have steep-sided cliffs with the rover going in the shallower valleys between them," the co-chair of the landing site working group explained.
Drop-down mock-upGale was selected after a rigorous investigation of some 60 competing sites. The selection process took five years and involved about 150 researchers.
High-resolution imagery was acquired of the best sites, and Nasa even built models of some of the site surfaces and dropped a simulation rover on to them to assess their suitability.
Michael Watkins, the mission's project engineer, said the expected precision of the new entry, descent and landing system meant that the space agency could have chosen any of the top contenders.
"We can control the lift of the vehicle a little bit during entry and we can cancel out some unexpected differences in atmospheric drag that would cause the landing zone to be large," he told reporters.
"Previous missions have had landing zones that have been up to 10 times larger than MSL. MSL is going to land in a 20km-across spot."
MSL-Curiosity has been funded for an initial surface mission of two years. But the fact that Nasa's Opportunity rover continues to roll across the Red Planet today, seven years after landing, suggests the new vehicle may have a very long life ahead of it. What is more, the new vehicle carries a nuclear battery that will provide ample power on a planet where dust storms can blight the operation of solar panels.
MSL-Curiosity is currently being prepared for its November launch at Nasa's Kennedy Space Center.
22/07/2011 - Space shuttle Atlantis makes final landing
Space shuttle Atlantis has landed back on Earth, bringing to a close America's 30-year orbiter programme.
The vehicle swept into the Kennedy Space Center, its wheels touching the runway just before local sunrise.
Nasa's shuttles were instrumental in building the space station, and were used to maintain the Hubble telescope.
"The space shuttle changed the way we view the world and it changed the way we view the Universe," said commander Chris Ferguson on landing.
"There's a lot of emotion today but one thing's indisputable: America's not going to stop exploring," he radioed to mission control.
Retirement of Nasa's iconic shuttle fleet was ordered by the US government, in part due to the high cost of maintaining the ships.
The decision leaves the country with no means of putting astronauts in orbit.The US space agency's intention is to invite the private sector to provide it with space transport services, and a number of commercial ventures already have crew ships in development.
These are unlikely to be ready to fly for at least three or four years, however.
In the interim, Nasa will rely on the Russians to ferry its people to and from the International Space Station (ISS).
Despite the dark skies over Florida's Space Coast, large crowds came out to try to glimpse Atlantis as it made its historic return from orbit. Two thousand people were gathered at Kennedy's landing strip itself, but even in at the Johnson Space Center in Texas, where mission control is sited, they came in huge numbers.
The de-orbit track brought Atlantis across central Florida and the Titusville-Mims area before a hard bank to the left put the vehicle on a line to Runway 15 at Kennedy.
Commander Ferguson, a veteran of two previous shuttle missions was at the controls, with his pilot Doug Hurley alongside him. Mission specialists Sandy Magnus and Rex Walheim were sitting directly behind on the flightdeck.
Their ship's rear wheels touched the ground at 0556 local time (0956 GMT; 1056 BST), and the vehicle was stationary under a minute later.It concluded a 13-day re-supply mission to the ISS.
The return of Atlantis marked a moment of high emotion for the Space Coast - not least because it will trigger a big lay-off of contractor staff. More than 3,000 people involved in shuttle operations lose their jobs this week.
Mindful of this, Nasa Administrator and former astronaut Charles Bolden was quick to thank programme staff in the speeches that followed the landing.
"I want everybody who was involved in this to feel incredibly proud of what you did and what your role was," he said.
"Like me, [the crew of Atlantis] got to do the flying but we owe an incredible debt of gratitude to the thousands, literally tens of thousands, of folks all around the country who made all this possible."
The orbiter programme does not officially end for a month, but even then it is likely to take a couple of years to close all activities, such as the archiving of decades of shuttle engineering data.
For Atlantis, its retirement will be spent as a static display at the Kennedy visitor complex.
The Discovery and Endeavour shuttles, which made their final flights earlier this year, will go to the Air and Space Museum's Udvar-Hazy Center in Virginia and the California Science Center in Los Angeles, respectively
Nasa hopes to invest money saved from shuttle operations in a new spaceship and rocket that can take humans beyond the ISS to destinations such as the Moon, asteroids and Mars.
The conical ship, known as Orion, has already been defined and is in an advanced stage of development. The rocket, on the other hand, is still an unknown quantity.
The US Congress has told the agency what its minimum capabilities should be. However, the agency is currently struggling to put those specifications into a concept it says can be built to the timeline and budget specified by the politicians.
It promises to detail the rocket's baseline design before the summer is out.
21/07/2011 - A cosmic superbubble dominates a stellar nursery
The European Southern Observatory’s (ESO) Very Large Telescope (VLT) captured this striking view of the nebula around the star cluster NGC 1929 within the Large Magellanic Cloud (LMC), a satellite galaxy of our Milky Way. A colossal example of what astronomers call a superbubble dominates this stellar nursery. It is being carved by the winds from bright young stars and the shock waves from supernovae explosions.
The LMC is a small neighboring galaxy to the Milky Way. It contains many regions where clouds of gas and dust are forming new stars. One such region, surrounding the star cluster NGC 1929, is shown close-up in this new image from ESO’s VLT. This nebula is officially known as LHA 120-N 44 (N 44). Hot young stars in NGC 1929 are emitting intense ultraviolet light and causing the gas to glow. This effect highlights the aptly named superbubble, a vast shell of material around 325 by 250 light-years across. For comparison, the nearest star to our Sun is just over 4 light-years distant.
The N 44 superbubble has been produced by the combination of two processes. First, stellar winds — streams of charged particles from the hot and massive stars in the central cluster — cleared out the central region. Then, massive cluster stars that exploded as supernovae created shock waves and pushed the gas out farther to form the glowing bubble.
Although destructive forces shaped the superbubble, new stars are forming around the edges where the gas is being compressed. Like recycling on a cosmic scale, this next generation of stars will breathe fresh life into NGC 1929.
21/07/2011 - Stellar thief’s secret stash uncovered
The Large Magellanic Cloud (LMC) has been caught red-handed as the perpetrator of a stellar crime involving the theft of hundreds of stars from the Small Magellanic Cloud (SMC), by astronomical detectives from the National Optical Astronomy Observatory (NOAO) and their collaborators at the University of Arizona and the Space Telescope Science Institute.
The LMC and SMC are both neighbouring galaxies to our Milky Way and lie at distances of around 160,000 and 200,000 light years away where they are easily visible to the unaided eye from the southern hemisphere.With the analysis of approximately 5900 giant and supergiant stars in the LMC galaxy, NOAO astronomers Knut Olsen and Bob Blum alongside their collaborators Dennis Zaritsky (University of Arizona) and Martha Boyer and Karl Gordon (Space Telescope Science Institute) uncovered that over 5% of observed stars residing in the LMC are rotating counter to the rest of the stars that make up the galaxy, or perhaps in a plane that is greatly inclined to the rotation of the LMC. The stars’ unusual orbits indicate that they were not formed from the rotation and eventual collapse of a cloud of gas that is believed to have formed the LMC, an irregular galaxy which houses the Tarantula Nebula, the most active star-forming region in our Local Group.
Despite their findings, however, an ambiguity still remains; the astronomers were only able to measure the projection of stellar velocities into the line of sight, and no other directions in which the stars choose to move. “We think that the stolen stars have such peculiar velocities because they were stripped from the SMC in its interaction with the LMC,” says Olsen. “Gurtina Besla, a graduate student at Harvard, has done a computer simulation of the interaction and has demonstrated that the LMC and SMC passed very close to each other about 1.2 billion years ago and, in the process, pulled out a long stream of hydrogen gas from the SMC [the Magellanic Stream]. We suspect that the same event pulled out these stars.”
Under closer examination, the counter-rotating stars admitted another anomaly. The chemical composition of these stars were different in comparison to the make-up of the other stars which rest within the large cloud. “Their chemical abundances don’t match those usually found in the LMC,” adds Olsen. “These stars are poorer in iron; but they do match the chemical abundances of the SMC.”
Armed with these pieces of evidence, the research team concluded that the galaxy was guilty of stealing stars from the SMC by its superior gravitational pull. Using the multi-object spectrometer on the Cerro Tololo Inter-American Observatory 4-metre Bianco Telescope in Chile to observe 4600 stars, the astronomers were able to observe their spectral characteristics simultaneously, finally combing these observations with data on 1300 other stars in their search for the uncovered pattern. “It is not always easy to tell whether the stars in a galaxy formed in the galaxy or formed somewhere else and then were captured,” says Olsen. “Since the LMC is so close to us, we were able to observe a large number of individual stars and to our surprise, the LMC contained a significant number of stars that must have formed elsewhere.”
The Spitzer Space Telescope also proved useful for making infrared observations in the team’s investigation of how stars form and evolve in the LMC – a very important angle from which the scientists had to approach. “Using observations with the Spitzer Space Telescope, we are able to get a complete census of the stellar populations in the LMC,” says Deputy Director Bob Blum. “With the ground-based observations we could determine the properties and motions of a large sample of stars throughout the galaxy. By combining both, we were able to tell that some of the stars must have come from the neighbouring SMC. This led to a deeper understanding of how galaxies can and do interact and change over time.”
This result could also help to explain the unusually large amount of star formation in the LMC in the Tarantula Nebula, named because of its appearance in a small telescope. If this region of star birth was in our Galaxy, lying as close as the Orion Nebula does (about 1,340 light years), then its glow would cast shadows on the ground due to its size. The stellar nursery is located where gas and captured stars torn from the SMC are colliding with the LMC’s own gas at high velocity. “We estimate the velocity with which the SMC gas hits the LMC to be about 50 to 100 km/s,” says Olsen. “We can’t know for sure, since we only observe the component of the velocity vector that is projected into the line of sight.” The shock wave that results from the collision pressurises the gas such that star formation is much more likely leading to bursts of large, unstable stars which can explode as supernova, where their older remnants can be identified with the help of X-ray telescopes.
21/07/2011 - Hubble discovers Pluto’s fourth moon
Astronomers using the Hubble Space Telescope to look for potential rings around dwarf planet Pluto have instead uncovered a fourth moon orbiting the distant icy world.
The moon, currently assigned the temporary name P4, is the smallest of Pluto’s satellites – astronomers estimate that its diameter is between 13 and 34 kilometres. The largest moon Charon is 1,043km wide and Nix and Hydra are in the range of 32-113 kilometres. P4 is located between the orbits of Nix and Hydra.“I find it remarkable that Hubble’s cameras enabled us to see such a tiny object so clearly from a distance of more than 5 billion kilometres,” says Mark Showalter of the SETI Institute, who led this Hubble observing program. The moon was first identified in a Wide Field Camera 3 image taken on 28 June, and confirmed in follow-up images snapped on 3 and 18 July. The new images had much longer exposure times than those previously taken of Pluto’s neighbourhood, which is why P4 has been overlooked until now.
The hunt for rings around Pluto stems from the idea that material blasted off Pluto’s moons by micrometeorite impacts may go into orbit around the planet. So far no evidence for the proposed ring has been identified, but the Hubble observations will continue to prime the New Horizons spacecraft for when it encounters the outer Solar System dwarf planets in 2015 for close-up investigation.
21/07/2011 - Shuttle Atlantis heads home for farewell
Space shuttle Atlantis is ready to make one last descent to Earth.
The orbiter and its crew of four are scheduled to hit the runway at the Kennedy Space Center in Florida just before sunrise on Thursday.
At "wheel-stop", the ship will complete its 13-day mission to the space station; but more significantly, it will close the book on Nasa's 30-year shuttle programme.
Atlantis, like Discovery and Endeavour before it, is being retired.
The US space agency is turning to the private sector for future astronaut transport services, hoping that a number of commercial ventures will emerge in the coming years to ferry crews to and from the low-Earth orbit.
Atlantis has two opportunities to land on Thursday, with the first timed at 0556 EDT (0956 GMT; 1056 BST). Weather forecasters expect conditions to be near perfect for the attempt.
Officials have resisted calls to target the second opportunity at 0733 and the better light it would afford shuttle fans to see the ship sweep in over Florida's Space Coast.
"We want to stick with what we do normally with our processes and procedures," said LeRoy Cain, the chair of the space shuttle's mission management team.
"Whether it's 40 minutes before sunrise or an hour after, it will be a good landing at Kennedy Space Center. We're going to stick with our plan."
Atlantis undocked from the International Space Station (ISS) on Tuesday. It had delivered some four tonnes of supplies to the platform, including a huge load of food.
Its landing is sure to be wound up with plenty of emotion - not least because it will trigger a big lay-off of contractor staff that have supported shuttle operations. More than 3,000 will be let go within days of touch-down.
The programme itself does not officially end for a month, but even then it is likely to take a couple of years to close all activities, such as the archiving of decades of shuttle engineering data.
For Atlantis, its retirement will be spent as a static display at the Kennedy visitors complex.
Assuming the ship takes the first landing opportunity on Thursday, its career statistics will read 33 flights, 307 days in space, logging 4,848 orbits, for a total distance travelled of 202,673,974km (125,935,769 miles).
Mind the gapThe end of the shuttle programme will leave a gap in America's astronaut-launch capability that is unlikely to be filled for at least three or four years.
In the short-term, the US will use Russian Soyuz rockets and capsules to fly its astronauts to the ISS.
A number of US national commercial carriers are then expected to enter service around the middle of the decade.
Nasa will buy seats in these astronaut "taxis". The vehicles are expected to be much simpler - and a lot cheaper - to operate than the shuttle.
"We're not asking industry to do anything cutting-edge here; what we're asking US industry to do is replicate the capabilities that were developed in the 1960s to do the relatively simple task of carrying a few people to orbit," said Dr John Logsdon, professor emeritus of the Space Policy Institute at The George Washington University. "That doesn't require new, or emerging or breakthrough technologies," he told BBC News.
This more commercial approach to low-Earth orbit activities is intended to free up resources for Nasa to build a new capsule and rocket that can take humans beyond the space station to destinations such as the Moon, asteroids and Mars.
The conical ship, known as Orion, has already been defined and is in an advanced stage of development. The rocket, on the other hand, is still an unknown quantity.
US Congress has told the agency what its minimum capabilities should be. However, Nasa is currently struggling to put those specifications into a concept it says can be built to the timeline and budget specified by the politicians. It promises to detail the rocket's baseline design before the summer is out.
19/07/2011 - Two brown dwarfs found in solar neighbourhood
Two ultracool brown dwarfs located only 15 and 18 light years away from the Sun have been discovered using the Wide-Field Infrared Survey Explorer.
The brown dwarfs were discovered by astronomers at the Leibniz Institute for Astrophysics Potsdam (AIP) using the Wide-Field Infrared Survey Explorer (WISE). The duo, dubbed WISE J0254+0223 and WISE J1741+2553, lie at 18 and 15 light years away respectively. While the closest known brown dwarf is only 12 light years away, the discovery of two new neighbours could mean that we are surrounded by these “failed stars” and that red dwarf star Proxima Centauri, at 4.2 light years away, might eventually have competition as the Sun’s nearest companion.Ralf-Dieter Scholz and his team at AIP used WISE to detect the brown dwarfs via their strong presence in the infrared. The brown dwarf pair also exhibit a high proper motion, that is, their position in the sky has changed from our point of view in a relatively short period of time – objects close to us are more likely to have an easily detectable proper motion.
Brown dwarfs are failed stars which were never hot enough and massive enough to initiate nuclear fusion. The letters OBAFGKM are assigned to ordinary stars in order to classify their spectral type, with O being the hottest and M being the coolest. Our Sun is a G type star with a temperature of 6,000 Kelvin. Brown dwarfs are cooler than M dwarfs and the letters L and T now follow M in the spectral sequence. The newly discovered brown dwarfs are “late type” T dwarfs, with a spectral type of between T8 and T10, meaning that they lie towards the cooler end of the T-class brown dwarfs. Another nearby brown dwarf, UGPS 0722, allows the temperature of the new brown dwarfs to be estimated. “The spectra of one of our objects, WISE 1741, and of the comparison T10 dwarf UGPS 0722 are very similar,” Scholz tells Astronomy Now. “Therefore we can assume a similar temperature [of] about 500 Kelvin. For our second object, WISE 0254, we have no spectroscopic observations so far, but I expect it to have a similar spectral type, hence a similar temperature.”
At a temperature of only 500 Kelvin, which is a typical oven temperature of 230 degrees Celsius, these brown dwarfs are so cool that they may even belong to the proposed Y-class brown dwarfs. “I would not exclude that these objects will later be classified as early Y dwarfs, once there are more of these ultracool brown dwarfs that will have been observed and the classification system for Y dwarfs will be established,” explains Scholz.
It is thought that brown dwarfs could contribute to some of the missing mass in the Universe, as they are very difficult to detect. However, Scholz says that this would not be a significant contribution. “I think that the contribution of brown dwarfs to baryonic dark matter remains very small (at most a few per cent), even if we will find in the future that the number of brown dwarfs is comparable to the number of stars. At the moment, we know about ten times less brown dwarfs than stars in the immediate solar neighbourhood.”
19/07/2011 - Asteroid Vesta reveals its scars
Nasa's Dawn spacecraft has returned some remarkable new imagery of the asteroid Vesta, now that it is safely in orbit around the 530km-wide rock.
The pictures reveal the ancient body's craters, slopes and grooves in detail that is far beyond the vision of Earth-bound telescopes, including Hubble.
Dawn scientists will have a busy year interpreting the asteroid's features.
They will be looking for some fresh insight on how such objects came into being 4.6 billion years ago.
It is often said the asteroids, which dominate a region of space between Mars and Jupiter, are the rubble that was left over after the planets proper had formed.
"We are beginning the study of arguably the oldest extant primordial surface in the Solar System," said Dawn's principal investigator Christopher Russell from the University of California, Los Angeles.
"This region of space has been ignored for far too long. So far, the images received to date reveal a complex surface that seems to have preserved some of the earliest events in Vesta's history, as well as logging the onslaught that Vesta has suffered in the intervening eons."
Dawn's quest at Vesta over the coming months is to undertake a comprehensive survey.
The probe carries instruments to detect the mineral and elemental composition of its surface rocks. It will be looking for evidence of geological processes such as mountain building and rifting. The Dawn science team is keen to understand how Vesta's surface has been remodelled over time by impacts and even lava flows.
Dawn's remote sensing instruments will also be able to discern something of the asteroid's internal structure. The expectation is that scientists will confirm it has a metallic core.
From the outside, Vesta looks like a punctured football, the result of a colossal collision sometime in its past that knocked off its south polar region.
Much the rock that was liberated in that mighty impact has found its way to Earth, falling to the ground as meteorites.
Dawn was launched by the US space agency almost four years ago.
The probe, which is propelled by an ion engine, allowed itself to be captured in the gravitational field of Vesta on Saturday.
Although initially orbiting the rock at several thousand km, Dawn will move closer over time - perhaps to within 200km if navigators are confident there is no risk to the spacecraft.
Once it has completed its work at Vesta, the probe will move on to the even bigger rock, Ceres. With a diameter of roughly 950km, this world has a much more rounded shape and is classed as a "dwarf planet", the same designation now ascribed to Pluto.
19/07/2011 - Atlantis shuttle undocks from space station
The US shuttle Atlantis has undocked from the International Space Station and is bound now for a final landing at the Kennedy Space Center.
When the orbiter reaches Earth on Thursday morning, it will bring to a close Nasa's 30-year re-usable spaceplane programme.
The shuttle pushed away from the station on schedule at 0628 GMT.
"Farewell ISS, make us proud," said Atlantis commander Chris Ferguson as his ship slipped away.
The shuttle moved to a point about 200m (600ft) off the bow of the platform, which then swung about 90 degrees using thrusters on its Russian stern.
The manoeuvre enabled Atlantis to fly over the 400-tonne structure, to take photographs along its truss, or backbone, and of the ends of some of the modules.
This imagery will help engineers on the ground to understand better how the various elements that make up the ISS are coping in the harsh environment of space.
Atlantis' crew of four had presented the station crew of six with two leaving presents before climbing aboard the orbiter and closing the hatch.
One was a model of the shuttle - a reminder of the pivotal role the vehicle has played in building the station. The other was a small American flag flown on the very first space shuttle mission in 1981.
This flag will be handed to the first American astronauts to reach the ISS on one of the privately operated space vehicles Nasa is now encouraging to replace the shuttle.
The moment of Atlantis' departure occurred some 400km above the Pacific Ocean, just east of Christchurch, New Zealand.
Undocking was sounded - as tradition would have it - by a bell being rung out on the station, and then speeches from Ferguson and Ron Garan, the lead Nasa resident on the outpost.
"Atlantis departing the International Space Station for the last time," Garan called out. "Thank you for your 12 docked missions to the ISS, and for capping off 37 space shuttle missions to construct this incredible orbiting research facility."
Ferguson replied: "As the ISS now enters the era of utilisation, we'll never forget the role played by the space shuttle in its creation. Like a proud parent, we anticipate great things to follow from the men and women who build, operate and live there."
Atlantis is set to touch down on Kennedy's runway at 0557 local time (0957 GMT) on Thursday.
It is carrying about 2.5 tonnes of unneeded materials and rubbish from the ISS.
Nasa's orbiter programme officially ends 30 days after wheel stop, although it will take about two years to close all activities, including the archiving of decades of engineering data.
Atlantis itself will be made safe for public display at the Kennedy visitors complex.
Shuttle retirement will leave a gap in America's astronaut-launch capability that is unlikely to be filled for at least three or four years.
In the short-term, the US will have to rely on Russian Soyuz rockets and capsules to get its men and women to and from the ISS.
Sometime mid-decade, the first of a range of commercial American launch vehicles should be ready to fly.
On Monday, Nasa signed an agreement with the Colorado-based United Launch Alliance company to assess its Atlas 5 rocket for crew operations.
The review will help determine whether the Atlas is fundamentally safe enough to lift humans into orbit.
15/07/2011 - Galaxy-Sized Twist in Time Pulls Violating Particles Back Into Line
A University of Warwick physicist has produced a galaxy-sized solution that explains one of the outstanding puzzles of particle physics, while leaving the door open to the related conundrum of why different amounts of matter and antimatter seem to have survived the birth of our Universe.
Physicists would like a neat universe where the laws of physics are so universal that every particle and its antiparticle behave in the same way.
However in recent years experimental observations of particles known as Kaons and B Mesons have revealed significant differences in how their matter and anti matter versions decay. This "Charge Parity violation" or "CP violation" is an awkward anomaly for some researchers but is a useful phenomenon for others as it may open up a way of explaining why more matter than anti matter appears to have survived the birth of our universe.
However Dr Mark Hadley, of the Department of Physics at the University of Warwick, believes he has found a testable explanation for apparent Charge Parity violation that preserves parity but also makes the Charge Parity violation an even more plausible explanation for the split between matter and antimatter.
Dr Hadley's paper (just published in EPL (Europhysics Letters) and entitled "The asymmetric Kerr metric as a source of CP violation") suggests that researchers have neglected the significant impact of the rotation of our Galaxy on the pattern of how sub atomic particles breakdown.
Dr Hadley says: "Nature is fundamentally asymmetric according to the accepted views of particle physics. There is a clear left right asymmetry in weak interactions and a much smaller CP violation in Kaon systems. These have been measured but never explained. This research suggests that the experimental results in our laboratories are a consequence of galactic rotation twisting our local space time. If that is shown to be correct then nature would be fundamentally symmetric after all. This radical prediction is testable with the data that has already been collected at Cern and BaBar by looking for results that are skewed in the direction that the galaxy rotates."
It is easy to neglect the effect of something as large as a galaxy because what seems most obvious to us is the local gravitation field of Earth or the Sun, both of which have a much more readily apparent gravitational affect on us than that exerted by our galaxy as a whole. However Dr Hadley believes that what is more important in this case is an affect generated by a spinning massive body.
The speed and angular momentum of such a massive spinning body creates "frame dragging" on its local space and time twisting the shape of that space time and creating time dilation effects.
The spin of our Galaxy has a twisting effect on our local space that is a million times stronger than that caused by Earth's spin.
When CP violation has been observed in the decay of B-Mesons the key difference observed between the break-up of matter and antimatter versions of the same particle is variation in the different decay rates. Curiously even though researchers observe that wide variation in the pattern of decay rates when those individual decay rates are added together they add up to the same total for both matter and antimatter versions of the same particle.
Dr Hadley believes that the "frame dragging" affect of the whole Galaxy explains all of those observations. Matter and antimatter versions of the same particle will retain exactly the same structure except that they will be mirror images of each other. It is not unreasonable to expect the decay of those particles to also begin as an exact mirror image of each other. However that is not how it ends. The decay may begin as a exact mirror image but the galactic frame dragging affect is significant enough to cause the different structures in each particle to experience different levels of time dilation and therefore decay in different ways. However the overall variation of the different levels of time dilation averages out when every particle in the decay is taken into account and CP violation disappears and parity is conserved.
The beauty of this theory is that it can also be tested. There are predictions that can be made and tested for. The massive array of data that already exists, that shows apparent CP violation in some decays, can be re-examined to see if it shows a pattern that is aligned with the rotation of the galaxy.
The paper only addressees how galactic scale frame dragging could explain experimental observations of apparent CP violation. However the explanation it provides also leaves open the door to those theorists who believe CP violation would be a useful tool to explain the separation of matter and antimatter at the birth of our universe and the subsequent apparent predominance of matter. Indeed that galactic scale frame dragging may even drag open that door a little wider. The universe's earliest structures, perhaps the very earliest, may have had sufficient mass and spin to generate frame dragging affects that could have had a significant effect the distribution of matter and antimatter.
15/07/2011 - Dawn probe set to orbit Asteroid Vesta
The US space agency says its Dawn probe should go into orbit around the Asteroid Vesta early on Saturday (GMT).
The robotic satellite will be spending a year at the 530km-wide body before moving on to the "dwarf planet" Ceres.
New pictures on Dawn's approach to Vesta show the giant rock in unprecedented detail.
The asteroid looks like a punctured football, the result of a colossal collision sometime in its past that knocked off its south polar region.
Vesta was discovered in 1807, the fourth asteroid to be identified in the great belt of rocky debris orbiting between Mars and Jupiter.
At the time, its great scale meant it was designated as another planet but it later lost this status as researchers learnt more about the diversity of objects in the Solar System.
Close but carefulDawn's encounter is occurring about 188 million km (117 million miles) from Earth.
The probe is propelled by an ion engine and engineers have put the spacecraft on a course to be captured in the gravitational field of Vesta.
They expect to hear confirmation from the satellite on Saturday that it is safely circling the rock.
Initially, Dawn will be about 16,000km (9,900 miles) from the asteroid, but this distance will be reduced over time.
Mission scientists hope to get within 200km of the surface but the team do not intend to take any unnecessary risks.
"We would like to get as low as possible but if we crash Dawn, Nasa would understandably be very angry at us," Principal Investigator Chris Russell told BBC News.
Asteroids can tell us about the earliest days of the Solar System. These wandering rocks are often described as the rubble that was left over after the planets proper had formed.
Vesta and Ceres should make for interesting subjects. They are both evolved bodies - objects that have heated up and started to separate into distinct layers.
Surface detail"We think that Vesta has a metal core in the centre - an iron core - and then silicate rock around it," explained Dr Russell.
"And then, sometime in its history, it got banged on the bottom and a lot of material was liberated. Some of this material gets pulled into the Earth's atmosphere. One in 20 meteorites seen to fall to Earth has been identified with Vesta," he added.
Ceres, which, at 950km in diameter, is by far the largest and most massive body in the asteroid belt, probably did not evolve as much as Vesta.
Scientists think it likely that it retains a lot of water, perhaps in a band of ice deep below the surface.
Dawn's quest at Vesta over the coming months will be to map the asteroid's surface. The probe carries instruments to detect the mineral and elemental abundances in its rocks. It will be looking for evidence of geological processes such as mountain building and rifting. The team is keen to understand how Vesta's surface has been remodelled over time by impacts and even lava flows.
12/07/2011 - Obama makes call to space station
US President Barack Obama joked with astronauts in a call to the International Space Station (ISS).
When he came on the line, the American leader said: "This is President Obama, who am I talking to?"
After the crew introduced themselves, he quipped: "Well, that's funny because I was just dialling out for pizza; I didn't expect to end up in space."
Mr Obama called the ISS to pay tribute to the crew of space shuttle Atlantis on its final visit to the station.
When Atlantis returns to Earth next Thursday, the ship will join the US space agency's (Nasa) other shuttles in retirement.
"There have been thousands who have poured their hearts and souls into America's space shuttle programme over the last three decades that are following this mission with special interest," the president observed. "To them and all the men and women of Nasa, I want to say thank you. You helped our country lead the space age and you continue to inspire us."
Mr Obama has set Nasa on a path to commercialising low-Earth orbit space transportation. He wants the next generation of American vehicles that taxi astronauts to and from the space station to be developed and operated by private companies.The first of these ships could fly in the next three to four years. As an incentive, the Atlantis crew will be leaving on station a special flag flown by the maiden shuttle mission back in 1981. The first commercial crew to arrive at the ISS will be able to claim it as a prize in what Mr Obama described as a "capture the flag moment for commercial spaceflight".
"We sure hope to see some of our commercial partners climbing onboard really soon," said Atlantis shuttle commander Chris Ferguson. "I know there is a lot of competition out there, a lot of people are fervently working towards this goal to be the first to send a commercial astronaut into orbit; and we look forward to seeing them here soon."
The Atlantis crew are in the midst of a very busy few days at the ISS. They brought up more than 3.5 tonnes of supplies, including over a tonne of food. All of it has to be transferred to permanent storage positions on the station, and then 2.5 tonnes of rubbish must be put inside the shuttle for the return to Earth.
Nasa has extended the mission by one day. Atlantis is due to land at the Kennedy Space Center in Florida early on 21 July local time.
"It's going to be sad to retire the shuttle," commander Ferguson said in an earlier call with the American media. "That said, it's had a very long and storied career. It's done tremendous things.
"If it weren't for the space shuttle, the station wouldn't be here and it certainly wouldn't be as large as it is." he added.
10/07/2011 - Shuttle Atlantis docks with space station for last time
Atlantis has docked with the International Space Station (ISS) on the final mission of the US space shuttle programme.
It will spend at least seven days at the ISS and, on its return to Earth, will be retired along with the other shuttles in Nasa's fleet.
Atlantis is taking vital supplies to the space station, including more than a tonne of food, ensuring astronauts there have got enough to last a year.
The first shuttle mission was in 1981.
RobotsAt 1507 GMT on Sunday, Nasa mission control in Houston announced: "Contact, docking confirmed."
The naval bell on the ISS chimed to greet Atlantis.
"Welcome to the International Space Station for the last time," ISS astronaut Ronald Garan said.
Atlantis commander Chris Ferguson replied: "It's great to be here station, see you shortly."
ISS astronauts photographed the shuttle as it did a backflip before docking, so that all of the craft can be studied for damage before its return to Earth.
Atlantis is carrying the Raffaello Multi-Purpose Logistics Module, a large cylinder containing more than 3.5 tonnes of food, other supplies and spare parts designed to sustain the station.
The cargo is to be lifted out of the shuttle's payload bay and attached directly to the station on Monday.
The Atlantis and ISS crews will then be able to go inside Raffaello to begin the process of transferring its contents to more permanent storage positions on the platform.
BBC science correspondent Jonathan Amos says the delivery has major significance.
Once Nasa retires its shuttles, it will be relying on robotic spacecraft from private companies to make cargo runs to the ISS, he says.
Just one spacewalk will be performed during this mission.
This will be done by two of the station's residents, who will move an ammonia pump that recently failed on the station to the shuttle's payload bay.
The pump is an important component in the ISS cooling system and it will be taken back down to the ground so engineers can understand why it stopped working.
Atlantis is due to return to Earth on 20 July, bringing to an end Nasa's 30-year orbiter programme.
06/07/2011 - Eye of Gaia: Billion-Pixel Camera to Map Milky Way
The largest digital camera ever built for a space mission has been painstakingly mosaicked together from 106 separate electronic detectors. The resulting "billion-pixel array" will serve as the super-sensitive 'eye' of ESA's Galaxy-mapping Gaia mission.
While the naked human eye can see several thousand stars on a clear night, Gaia will map a billion stars within our own Milky Way Galaxy and its neighbours over the course of its five-year mission from 2013, charting their brightness and spectral characteristics along with their three-dimensional positions and motions.
In order to detect distant stars up to a million times fainter than the eye can see, Gaia will carry 106 charge coupled devices (CCDs), advanced versions of chips within standard digital cameras.
Developed for the mission by e2v Technologies of Chelmsford, UK, these rectangular detectors are a little smaller than a credit card, each one measuring 4.7x6 cm but thinner than a human hair.
The 0.5x1.0 m mosaic has been assembled at the Toulouse facility of Gaia prime contractor Astrium France.
Technicians spent much of May carefully fitting together each CCD package on the support structure, leaving only a 1 mm gap between them. Working in double shifts in strict cleanroom conditions, they added an average four CCDs per day, finally completing their task on 1 June.
"The mounting and precise alignment of the 106 CCDs is a key step in the assembly of the flight model focal plane assembly," said Philippe Garé, ESA's Gaia payload manager.
The completed mosaic is arranged in seven rows of CCDs. The main array comprises 102 detectors dedicated to star detection. Four others check the image quality of each telescope and the stability of the 106.5º angle between the two telescopes that Gaia uses to obtain stereo views of stars.
In order to increase the sensitivity of its detectors, the spacecraft will maintain their temperature of -110º Celsius.
Gaia's CCD support structure, like much of the rest of the spacecraft, is made of silicon carbide -- a ceramic like material, extraordinarily resistant to deforming under temperature changes.
First synthesised as a diamond substitute, SiC has the advantage of low weight: the entire support structure with its detectors is only 20 kg.
Gaia will operate at the Earth-Sun L2 Lagrange point, 1,5 million kilometers behind Earth, when looking from the sun, where Earth's orbital motion balances out gravitational forces to form a stable point in space. As the spinning Gaia's two telescopes sweep across the sky, the images of stars in each field of view will move across the focal plane array, divided into four fields variously dedicated to star mapping, position and motion, colour and intensity and spectrometry.
Scheduled for launch in 2013, Gaia's three-dimensional star map will help to reveal the composition, formation and evolution of the Milky Way, sampling 1% of our Galaxy's stars.
Gaia should also sample large numbers of other celestial bodies, from minor bodies in our own Solar System to more distant galaxies and quasars near the edge of the observable Universe.
06/07/2011 - NASA's Hubble Makes One Millionth Science Observation
NASA's Hubble Space Telescope crossed another milestone in its space odyssey of exploration and discovery. On July 4, the Earth-orbiting observatory logged its one millionth science observation during a search for water in an exoplanet's atmosphere 1,000 light-years away.
"For 21 years Hubble has been the premier space science observatory, astounding us with deeply beautiful imagery and enabling ground-breaking science across a wide spectrum of astronomical disciplines," said NASA Administrator Charles Bolden. He piloted the space shuttle mission that carried Hubble to orbit. "The fact that Hubble met this milestone while studying a faraway planet is a remarkable reminder of its strength and legacy."
Although Hubble is best known for its stunning imagery of the cosmos, the millionth observation is a spectroscopic measurement, where light is divided into its component colors. These color patterns can reveal the chemical composition of cosmic sources.
Hubble's millionth exposure is of the planet HAT-P-7b, a gas giant planet larger than Jupiter orbiting a star hotter than our sun. HAT-P-7b, also known as Kepler 2b, has been studied by NASA's planet-hunting Kepler observatory after it was discovered by ground-based observations. Hubble now is being used to analyze the chemical composition of the planet's atmosphere.
We are looking for the spectral signature of water vapor. This is an extremely precise observation and it will take months of analysis before we have an answer," said Drake Deming of the University of Maryland and NASA's Goddard Space Flight Center in Greenbelt, Md. "Hubble demonstrated it is ideally suited for characterizing the atmospheres of exoplanets, and we are excited to see what this latest targeted world will reveal."
Hubble was launched April 24, 1990, aboard space shuttle's Discovery's STS-31 mission. Its discoveries revolutionized nearly all areas of astronomical research from planetary science to cosmology. The observatory has collected more than 50 terabytes of data to-date.
Hubble's odometer reading includes every observation of astronomical targets since its launch and observations used to calibrate its suite of instruments. Hubble made the millionth observation using its Wide Field Camera 3, a visible and infrared light imager with an on-board spectrometer. It was installed by astronauts during the Hubble Servicing Mission 4 in May 2009.
"The Hubble keeps amazing us with groundbreaking science," said Sen. Barbara A. Mikulski, the chairwoman of the Senate Commerce, Justice, Science and Related Agencies Appropriations Subcommittee that funds NASA. "I championed the mission to repair and renew Hubble not just to get one million science observations, but also to inspire millions of children across the planet to become our next generation of stargazers, scientists, astronauts and engineers."
"For 21 years Hubble has been the premier space science observatory, astounding us with deeply beautiful imagery and enabling ground-breaking science across a wide spectrum of astronomical disciplines," said NASA Administrator Charles Bolden. He piloted the space shuttle mission that carried Hubble to orbit. "The fact that Hubble met this milestone while studying a faraway planet is a remarkable reminder of its strength and legacy."
Although Hubble is best known for its stunning imagery of the cosmos, the millionth observation is a spectroscopic measurement, where light is divided into its component colors. These color patterns can reveal the chemical composition of cosmic sources.
Hubble's millionth exposure is of the planet HAT-P-7b, a gas giant planet larger than Jupiter orbiting a star hotter than our sun. HAT-P-7b, also known as Kepler 2b, has been studied by NASA's planet-hunting Kepler observatory after it was discovered by ground-based observations. Hubble now is being used to analyze the chemical composition of the planet's atmosphere.
We are looking for the spectral signature of water vapor. This is an extremely precise observation and it will take months of analysis before we have an answer," said Drake Deming of the University of Maryland and NASA's Goddard Space Flight Center in Greenbelt, Md. "Hubble demonstrated it is ideally suited for characterizing the atmospheres of exoplanets, and we are excited to see what this latest targeted world will reveal."
Hubble was launched April 24, 1990, aboard space shuttle's Discovery's STS-31 mission. Its discoveries revolutionized nearly all areas of astronomical research from planetary science to cosmology. The observatory has collected more than 50 terabytes of data to-date.
Hubble's odometer reading includes every observation of astronomical targets since its launch and observations used to calibrate its suite of instruments. Hubble made the millionth observation using its Wide Field Camera 3, a visible and infrared light imager with an on-board spectrometer. It was installed by astronauts during the Hubble Servicing Mission 4 in May 2009.
"The Hubble keeps amazing us with groundbreaking science," said Sen. Barbara A. Mikulski, the chairwoman of the Senate Commerce, Justice, Science and Related Agencies Appropriations Subcommittee that funds NASA. "I championed the mission to repair and renew Hubble not just to get one million science observations, but also to inspire millions of children across the planet to become our next generation of stargazers, scientists, astronauts and engineers."
06/07/2011 - Cassini Captures Images and Sounds of Saturn Storm
Scientists analysing data from NASA's Cassini spacecraft now have the first-ever, up-close details of a Saturn storm that is eight times the surface area of Earth.
On Dec. 5, 2010, Cassini first detected the storm that has been raging ever since. It appears approximately 35 degrees north latitude of Saturn. Pictures from Cassini's imaging cameras show the storm wrapping around the entire planet covering approximately 2 billion square miles (4 billion square kilometers).
The storm is about 500 times larger than the biggest storm previously seen by Cassini during several months from 2009 to 2010. Scientists studied the sounds of the new storm's lightning strikes and analyzed images taken between December 2010 and February 2011. Data from Cassini's radio and plasma wave science instrument showed the lightning flash rate as much as 10 times more frequent than during other storms monitored since Cassini's arrival to Saturn in 2004. The data appear in a paper published this week in the journal Nature.
"Cassini shows us that Saturn is bipolar," said Andrew Ingersoll, an author of the study and a Cassini imaging team member at the California Institute of Technology in Pasadena, Calif. "Saturn is not like Earth and Jupiter, where storms are fairly frequent. Weather on Saturn appears to hum along placidly for years and then erupt violently. I'm excited we saw weather so spectacular on our watch."
At its most intense, the storm generated more than 10 lightning flashes per second. Even with millisecond resolution, the spacecraft's radio and plasma wave instrument had difficulty separating individual signals during the most intense period. Scientists created a sound file from data obtained on March 15 at a slightly lower intensity period.
Cassini has detected 10 lightning storms on Saturn since the spacecraft entered the planet's orbit and its southern hemisphere was experiencing summer, with full solar illumination not shadowed by the rings. Those storms rolled through an area in the southern hemisphere dubbed "Storm Alley." But the sun's illumination on the hemispheres flipped around August 2009, when the northern hemisphere began experiencing spring.
"This storm is thrilling because it shows how shifting seasons and solar illumination can dramatically stir up the weather on Saturn," said Georg Fischer, the paper's lead author and a radio and plasma wave science team member at the Austrian Academy of Sciences in Graz. "We have been observing storms on Saturn for almost seven years, so tracking a storm so different from the others has put us at the edge of our seats."
The storm's results are the first activities of a new "Saturn Storm Watch" campaign. During this effort, Cassini looks at likely storm locations on Saturn in between its scheduled observations. On the same day that the radio and plasma wave instrument detected the first lightning, Cassini's cameras happened to be pointed at the right location as part of the campaign and captured an image of a small, bright cloud. Because analysis on that image was not completed immediately, Fischer sent out a notice to the worldwide amateur astronomy community to collect more images. A flood of amateur images helped scientists track the storm as it grew rapidly, wrapping around the planet by late January 2011.
The new details about this storm complement atmospheric disturbances described recently by scientists using Cassini's composite infrared spectrometer and the European Southern Observatory's Very Large Telescope. The storm is the biggest observed by spacecraft orbiting or flying by Saturn. NASA's Hubble Space Telescope captured images in 1990 of an equally large storm.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory in Pasadena manages the mission for the agency's Science Mission Directorate in Washington. The radio and plasma wave science team is based at the University of Iowa, Iowa City, where the instrument was built. The imaging team is based at the Space Science Institute in Boulder, Colo. JPL is a division of the California Institute of Technology, Pasadena.
For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini
On Dec. 5, 2010, Cassini first detected the storm that has been raging ever since. It appears approximately 35 degrees north latitude of Saturn. Pictures from Cassini's imaging cameras show the storm wrapping around the entire planet covering approximately 2 billion square miles (4 billion square kilometers).
The storm is about 500 times larger than the biggest storm previously seen by Cassini during several months from 2009 to 2010. Scientists studied the sounds of the new storm's lightning strikes and analyzed images taken between December 2010 and February 2011. Data from Cassini's radio and plasma wave science instrument showed the lightning flash rate as much as 10 times more frequent than during other storms monitored since Cassini's arrival to Saturn in 2004. The data appear in a paper published this week in the journal Nature.
"Cassini shows us that Saturn is bipolar," said Andrew Ingersoll, an author of the study and a Cassini imaging team member at the California Institute of Technology in Pasadena, Calif. "Saturn is not like Earth and Jupiter, where storms are fairly frequent. Weather on Saturn appears to hum along placidly for years and then erupt violently. I'm excited we saw weather so spectacular on our watch."
At its most intense, the storm generated more than 10 lightning flashes per second. Even with millisecond resolution, the spacecraft's radio and plasma wave instrument had difficulty separating individual signals during the most intense period. Scientists created a sound file from data obtained on March 15 at a slightly lower intensity period.
Cassini has detected 10 lightning storms on Saturn since the spacecraft entered the planet's orbit and its southern hemisphere was experiencing summer, with full solar illumination not shadowed by the rings. Those storms rolled through an area in the southern hemisphere dubbed "Storm Alley." But the sun's illumination on the hemispheres flipped around August 2009, when the northern hemisphere began experiencing spring.
"This storm is thrilling because it shows how shifting seasons and solar illumination can dramatically stir up the weather on Saturn," said Georg Fischer, the paper's lead author and a radio and plasma wave science team member at the Austrian Academy of Sciences in Graz. "We have been observing storms on Saturn for almost seven years, so tracking a storm so different from the others has put us at the edge of our seats."
The storm's results are the first activities of a new "Saturn Storm Watch" campaign. During this effort, Cassini looks at likely storm locations on Saturn in between its scheduled observations. On the same day that the radio and plasma wave instrument detected the first lightning, Cassini's cameras happened to be pointed at the right location as part of the campaign and captured an image of a small, bright cloud. Because analysis on that image was not completed immediately, Fischer sent out a notice to the worldwide amateur astronomy community to collect more images. A flood of amateur images helped scientists track the storm as it grew rapidly, wrapping around the planet by late January 2011.
The new details about this storm complement atmospheric disturbances described recently by scientists using Cassini's composite infrared spectrometer and the European Southern Observatory's Very Large Telescope. The storm is the biggest observed by spacecraft orbiting or flying by Saturn. NASA's Hubble Space Telescope captured images in 1990 of an equally large storm.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory in Pasadena manages the mission for the agency's Science Mission Directorate in Washington. The radio and plasma wave science team is based at the University of Iowa, Iowa City, where the instrument was built. The imaging team is based at the Space Science Institute in Boulder, Colo. JPL is a division of the California Institute of Technology, Pasadena.
For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini
05/07/2011 - The excitement of 'new space'
Like all would-be space entrepreneurs, David Thompson needed a big idea to get his business going.
Having worked on the development of the shuttle, he thought there might be something interesting one could usefully do with the vehicles' giant external fuel tanks.
These behemoths are dumped once the orbiters have made it into space and fall back into the atmosphere to be destroyed.
Thompson's brainwave was to push them into orbit, also.
His vision was for them to be filled with water. Over time, the tanks would then use electrolysis to split the liquid into hydrogen and oxygen - to produce yet more rocket fuel. A "gas station in the sky".
"There were a number of problems with this idea," Thompson recalls with a grin - "the number one being that there weren't that many rockets coming along this road where our gas station would be."
Undeterred, he simply moved on to his next concept.
The Pegasus rocket is dropped from an aeroplane before igniting its engine This was a booster module that would carry a satellite deployed from the shuttle into its correct orbit high above the Earth. This time, the spark caught hold and our space entrepreneur was off and running.
The Transfer Orbit Stage was the first product of the Orbital Sciences Corporation, now of Dulles, Virginia, the company set up by Thompson and two friends.
Today, there are no mad-cap ideas - just solid business practice that has turned the company into an established player in the space market, and one that now aims to play a significant role in the new commercial approach to human spaceflight being adopted by Nasa.
I caught up with David Thompson in London where he was being presented with an Arthur C Clarke Foundation award to recognise his achievements.
Sir Arthur, he told me, had been a major inspiration and receiving the award was a big thrill:
"We've been in business for over 29 years now but go back twice as many years and Sir Arthur was anticipating many of the technological innovations and practical applications of satellite technology that we've now had the chance to develop.
The Orbital-built Dawn probe is bearing down on the Vesta asteroid "It's amazing how many of his projections have become fact. For example, he projected communications and broadcasting would be the biggest commercial applications of space, and here we are today with - depending on what you count and how you count it - $100-150bn a year tied up in that business. He was astonishing."
For those who don't follow space matters closely, Orbital may not be as familiar a space name as, say, Boeing or Lockheed Martin. But the Dulles outfit has built a formidable reputation.
Its mainstays are rockets and lightweight satellites. To date it has launched about 700 of the former and built and delivered around 150 of the latter.
Perhaps, Orbital's best known launcher is Pegasus - an innovative booster that is carried to altitude by an aeroplane before firing its own engine to get above the atmosphere.
And listen out for Dawn, an OSC satellite that will make big news in the coming weeks. Dawn, which was constructed for Nasa, is fast approaching Vesta, a giant asteroid. The pictures it sends back to Earth are sure to be plastered all over the newspapers and the internet.
It's an interesting moment to be talking to David Thompson. In his younger days he spent some time working inside Nasa, but then went outside the agency to see if there was a different way to do space other than through Big Government. And in one sense, Nasa is now catching him up.
The Transfer Orbit Stage was more practical than a 'gas station in the sky' Once it retires its shuttle fleet following the final mission of Atlantis this month, the agency will be hiring OSC and other companies to service the International Space Station (ISS). Just as an organisation might contract an external provider to do its payroll or IT, so Nasa is going to contract private companies to ferry astronauts and cargo to and from the ISS.
OSC has teamed up with Thales Alenia Space (Italy) to build a robotic freighter called Cygnus. It won't have anything like the mass-carrying capability of a shuttle but the supplies it brings to the station will be critical to the outpost's future operation.
Its contract with Nasa is for a fixed price. Gone is the agency's old way of doing business which saw it pay companies what it cost to do the job, with a bit extra on top. Under the new arrangement, Orbital has to meet certain milestones to get its payments. If it doesn't make the grade, there'll be no cheques arriving in Dulles.
"I find it exciting and enlightened that a government agency that pioneered this area more than any other single organisation should conclude that the private sector is ready for this responsibility," said Thompson.
"It's not going to be without its difficulties and challengers but space has always been that way. It's an approach I believe will ultimately succeed and allow Nasa to invest its funds in more advanced missions that go to deep-space destinations."
Right now, the first Cygnus is being assembled and should be flying within months. First, however, there is the small matter of proving the rocket that Orbital intends to use to loft Cygnus. Called the Taurus II, it will make a maiden flight towards the end of the year.
Orbital's proposal for a shuttle-like vehicle to take crew to the ISS did not win over Nasa Not everything has gone exactly to plan: a development engine caught fire whilst on a test stand in June. Indeed, there's been a few knocks of late for Orbital. In March, it lost the Glory climate satellite when an Orbital rocket malfunctioned just minutes into its flight. Tough lessons, according to Thompson: "Having launched the number of rockets we have and made the number of satellite we have - we know such problems can be identified and solved, and that we can move on and be a little smarter next time."
Cygnus is an unmanned ship but Orbital has drawn up plans for a small shuttle-like vehicle it thinks could ferry astronauts to the ISS, also. Unfortunately for Orbital, Nasa has decided to invest in other companies' designs for human transportation. Thompson, though, hasn't ruled out competing again at a later date.
"The level of demand over the next decade for commercial astronaut transportation is probably not sufficient to support more than two, and possibly only one, operator," he told me.
"If Nasa has decided to focus on other areas, we may just have to take a pass this time around and continue to watch how things evolve."
David Thompson's Arthur C Clarke Award was formally announced at the UK Space Conference on Monday night in Coventry.
I'm afraid neither the OSC chairman nor this correspondent could be present in person. My excuse is that I've made the trip out to Cape Canaveral to watch the final launch of Atlantis - to see baton being passed from "old space" to "new space". (BBC News)
05/07/2011 - Atlantis shuttle crew arrive in Florida
The four US astronauts who will crew the last ever space shuttle mission have arrived in Florida.
The three men and one woman will launch in the Atlantis orbiter on Friday from the Kennedy Space Center.
Bumper crowds are expected on the Space Coast to watch the 1126 local time (1526 GMT) lift-off.
The US space agency (Nasa) is retiring its shuttles to make way for crew and cargo transportation services that will be operated by private companies.
Atlantis will be hauling more than 3.5 tonnes (8,000lb) of supplies to the International Space Station (ISS).
This load includes a year's worth of food. It should give Nasa some room to play with if the new commercial players have difficulty meeting their contractual obligations.
The four Atlantis astronauts - Commander Chris Ferguson, Pilot Doug Hurley, and Mission Specialists Sandy Magnus and Rex Walheim - flew into Kennedy from their training base in Houston, Texas.
As it was Independence Day here in the US, they had no hesitation in waving the Stars and Stripes for the photographers.
"This is a day that is decidedly American," said Commander Ferguson. "We have an eventful 12-day mission ahead of us… and when it's all over I think I can speak for everyone when I say we'll be very proud to put the right-hand book-end on the space shuttle programme."
Pilot Hurley added: "We want to thank the team that processed the Atlantis shuttle for her last flight. We just want to honour the entire Kennedy team that has worked on these magnificent machines these last 30-plus years."
The 8 July ascent will be the 135th shuttle launch and the 33rd of Atlantis.
In total, 355 individuals will have flown 852 times on those 135 missions since the very first shuttle flight on 12 April, 1981.
The five orbiters used over the course of the programme have flown 864,401,200km (537,114,016 miles) - a distance roughly similar to travelling from the Earth to the Sun and back three times.
Atlantis will add a further 6.5 million km (four million miles) to that total.
Discovery was the first ship to begin the run-down with a final flight in March, followed by Endeavour which landed one last time on 1 June.
The vehicles are all being retired to museums. Atlantis will end its days at the Kennedy Space Center visitor complex. (BBC News)
03/07/2011 - NASA's Spitzer Finds Distant Galaxies Grazed On Gas
This split view shows how a normal spiral galaxy around our local universe (left) might have looked back in the distant universe, when astronomers think galaxies would have been filled with larger populations of hot, bright stars (right).
Galaxies once thought of as voracious tigers are more like grazing cows, according to a new study using NASA's Spitzer Space Telescope. Astronomers have discovered that galaxies in the distant, early universe continuously ingested their star-making fuel over long periods of time. This goes against previous theories that the galaxies devoured their fuel in quick bursts after run-ins with other galaxies."Our study shows the merging of massive galaxies was not the dominant method of galaxy growth in the distant universe," said Ranga-Ram Chary of NASA's Spitzer Science Center at the California Institute of Technology in Pasadena, Calif. "We're finding this type of galactic cannibalism was rare. Instead, we are seeing evidence for a mechanism of galaxy growth in which a typical galaxy fed itself through a steady stream of gas, making stars at a much faster rate than previously thought."
Chary is the principal investigator of the research, appearing in the Aug. 1 issue of the Astrophysical Journal. According to his findings, these grazing galaxies fed steadily over periods of hundreds of millions of years and created an unusual amount of plump stars, up to 100 times the mass of our sun.
"This is the first time that we have identified galaxies that supersized themselves by grazing," said Hyunjin Shim, also of the Spitzer Science Center and lead author of the paper. "They have many more massive stars than our Milky Way galaxy."
Galaxies like our Milky Way are giant collections of stars, gas and dust. They grow in size by feeding off gas and converting it to new stars. A long-standing question in astronomy is: Where did distant galaxies that formed billions of years ago acquire this stellar fuel? The most favored theory was that galaxies grew by merging with other galaxies, feeding off gas stirred up in the collisions.
Chary and his team addressed this question by using Spitzer to survey more than 70 remote galaxies that existed 1 to 2 billion years after the Big Bang (our universe is approximately 13.7 billion years old). To their surprise, these galaxies were blazing with what is called H alpha, which is radiation from hydrogen gas that has been hit with ultraviolet light from stars. High levels of H alpha indicate stars are forming vigorously. Seventy percent of the surveyed galaxies show strong signs of H alpha. By contrast, only 0.1 percent of galaxies in our local universe possess this signature.
Previous studies using ultraviolet-light telescopes found about six times less star formation than Spitzer, which sees infrared light. Scientists think this may be due to large amounts of obscuring dust, through which infrared light can sneak. Spitzer opened a new window onto the galaxies by taking very long-exposure infrared images of a patch of sky called the GOODS fields, for Great Observatories Origins Deep Survey.
Further analyses showed that these galaxies furiously formed stars up to 100 times faster than the current star-formation rate of our Milky Way. What's more, the star formation took place over a long period of time, hundreds of millions of years. This tells astronomers that the galaxies did not grow due to mergers, or collisions, which happen on shorter timescales. While such smash-ups are common in the universe -- for example, our Milky Way will merge with the Andromeda galaxy in about 5 billion years -- the new study shows that large mergers were not the main cause of galaxy growth. Instead, the results show that distant, giant galaxies bulked up by feeding off a steady supply of gas that probably streamed in from filaments of dark matter.
Chary said, "If you could visit a planet in one of these galaxies, the sky would be a crazy place, with tons of bright stars, and fairly frequent supernova explosions."
NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages the Spitzer Space Telescope mission for the agency's Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at Caltech. Caltech manages JPL for NASA.
Chary is the principal investigator of the research, appearing in the Aug. 1 issue of the Astrophysical Journal. According to his findings, these grazing galaxies fed steadily over periods of hundreds of millions of years and created an unusual amount of plump stars, up to 100 times the mass of our sun.
"This is the first time that we have identified galaxies that supersized themselves by grazing," said Hyunjin Shim, also of the Spitzer Science Center and lead author of the paper. "They have many more massive stars than our Milky Way galaxy."
Galaxies like our Milky Way are giant collections of stars, gas and dust. They grow in size by feeding off gas and converting it to new stars. A long-standing question in astronomy is: Where did distant galaxies that formed billions of years ago acquire this stellar fuel? The most favored theory was that galaxies grew by merging with other galaxies, feeding off gas stirred up in the collisions.
Chary and his team addressed this question by using Spitzer to survey more than 70 remote galaxies that existed 1 to 2 billion years after the Big Bang (our universe is approximately 13.7 billion years old). To their surprise, these galaxies were blazing with what is called H alpha, which is radiation from hydrogen gas that has been hit with ultraviolet light from stars. High levels of H alpha indicate stars are forming vigorously. Seventy percent of the surveyed galaxies show strong signs of H alpha. By contrast, only 0.1 percent of galaxies in our local universe possess this signature.
Previous studies using ultraviolet-light telescopes found about six times less star formation than Spitzer, which sees infrared light. Scientists think this may be due to large amounts of obscuring dust, through which infrared light can sneak. Spitzer opened a new window onto the galaxies by taking very long-exposure infrared images of a patch of sky called the GOODS fields, for Great Observatories Origins Deep Survey.
Further analyses showed that these galaxies furiously formed stars up to 100 times faster than the current star-formation rate of our Milky Way. What's more, the star formation took place over a long period of time, hundreds of millions of years. This tells astronomers that the galaxies did not grow due to mergers, or collisions, which happen on shorter timescales. While such smash-ups are common in the universe -- for example, our Milky Way will merge with the Andromeda galaxy in about 5 billion years -- the new study shows that large mergers were not the main cause of galaxy growth. Instead, the results show that distant, giant galaxies bulked up by feeding off a steady supply of gas that probably streamed in from filaments of dark matter.
Chary said, "If you could visit a planet in one of these galaxies, the sky would be a crazy place, with tons of bright stars, and fairly frequent supernova explosions."
NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages the Spitzer Space Telescope mission for the agency's Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at Caltech. Caltech manages JPL for NASA.
03/07/2011 - Making a Spectacle of Star Formation in Orion
Best known as Messier 78, the two round greenish nebulae are actually cavities carved out of the surrounding dark dust clouds
Looking like a pair of eyeglasses only a rock star would wear, a new nebula view brings into focus a murky region of star formation. NASA's Spitzer Space Telescope exposes the depths of this dusty nebula with its infrared vision, showing stellar infants that are lost behind dark clouds when viewed in visible light. Best known as Messier 78, the two round greenish nebulae are actually cavities carved out of the surrounding dark dust clouds. The extended dust is mostly dark, even to Spitzer's view, but the edges show up in mid-wavelength infrared light as glowing, red frames surrounding the bright interiors. Messier 78 is easily seen in small telescopes in the constellation of Orion, just to the northeast of Orion's belt, but looks strikingly different, with dominant, dark swaths of dust. Spitzer's infrared eyes penetrate this dust, revealing the glowing interior of the nebulae.The light from young, newborn stars are starting to carve out cavities within the dust, and eventually, this will become a larger nebula like the "green ring" imaged by Spitzer.
A string of baby stars that have yet to burn their way through their natal shells can be seen as red pinpoints on the outside of the nebula. Eventually these will blossom into their own glowing balls, turning this two-eyed eyeglass into a many-eyed monster of a nebula.
This is a three-color composite that shows infrared observations from two Spitzer instruments. Blue represents 3.6- and 4.5-micron light, and green shows light of 5.8 and 8 microns, both captured by Spitzer's infrared array camera. Red is 24-micron light detected by Spitzer's multiband imaging photometer.
03/07/2011 - 'Odd Couple' Binary Star System Makes Dual Gamma-Ray Flares
This diagram, which illustrates the view from Earth, shows the binary's anatomy as well as key events in the pulsar's recent close approach.
In December 2010, a pair of mismatched stars in the southern constellation Crux whisked past each other at a distance closer than Venus orbits the sun. The system possesses a so-far unique blend of a hot and massive star with a compact fast-spinning pulsar. The pair's closest encounters occur every 3.4 years and each is marked by a sharp increase in gamma rays, the most extreme form of light. The unique combination of stars, the long wait between close approaches, and periods of intense gamma-ray emission make this system irresistible to astrophysicists. Now, a team using NASA's Fermi Gamma-ray Space Telescope to observe the 2010 encounter reports that the system displayed fascinating and unanticipated activity.
"Even though we were waiting for this event, it still surprised us," said Aous Abdo, a Research Assistant Professor at George Mason University in Fairfax, Va., and a leader of the research team.
Few pairings in astronomy are as peculiar as high-mass binaries, where a hot blue-white star many times the sun's mass and temperature is joined by a compact companion no bigger than Earth -- and likely much smaller. Depending on the system, this companion may be a burned-out star known as a white dwarf, a city-sized remnant called a neutron star (also known as a pulsar) or, most exotically, a black hole.
Just four of these "odd couple" binaries were known to produce gamma rays, but in only one of them did astronomers know the nature of the compact object. That binary consists of a pulsar designated PSR B1259-63 and a 10th-magnitude Be-type star known as LS 2883. The pair lies 8,000 light-years away.
The pulsar is a fast-spinning neutron star with a strong magnetic field. This combination powers a lighthouse-like beam of energy, which astronomers can easily locate if the beam happens to sweep toward Earth. The beam from PSR B1259-63 was discovered in 1989 by the Parkes radio telescope in Australia. The neutron star is about the size of Washington, D.C., weighs about twice the sun's mass, and spins almost 21 times a second.
The pulsar follows an eccentric and steeply inclined orbit around LS 2883, which weighs roughly 24 solar masses and spans about nine times its size. This hot blue star sits embedded in a disk of gas that flows out from its equatorial region.
At closest approach, the pulsar passes less than 63 million miles from its star -- so close that it skirts the gas disk around the star's middle. The pulsar punches through the disk on the inbound leg of its orbit. Then it swings around the star at closest approach and plunges through the disk again on the way out.
"During these disk passages, energetic particles emitted by the pulsar can interact with the disk, and this can lead to processes that accelerate particles and produce radiation at different energies," said study co-author Simon Johnston of the Australia Telescope National Facility in Epping, New South Wales. "The frustrating thing for astronomers is that the pulsar follows such an eccentric orbit that these events only happen every 3.4 years."
In anticipation of the Dec. 15, 2010, closest approach, astronomers around the world mounted a multiwavelength campaign to observe the system over a broad energy range, from radio wavelengths to the most energetic gamma rays detectable. The observatories included Fermi and NASA's Swift spacecraft; the European space telescopes XMM-Newton and INTEGRAL; the Japan-U.S. Suzaku satellite; the Australia Telescope Compact Array; optical and infrared telescopes in Chile and South Africa; and the High Energy Stereoscopic System (H.E.S.S.), a ground-based observatory in Namibia that can detect gamma rays with energies of trillions of electron volts, beyond Fermi's range. (For comparison, the energy of visible light is between two and three electron volts.)
"When you know you have a chance of observing this system only once every few years, you try to arrange for as much coverage as you can," said Abdo, the principal investigator of the NASA-funded international campaign. "Understanding this system, where we know the nature of the compact object, may help us understand the nature of the compact objects in other, similar systems."
Despite monitoring of the system with the EGRET telescope aboard NASA's Compton Gamma-Ray Observatory in the 1990s, gamma-ray emission in the billion-electron-volt (GeV) energy range had never been seen from the binary.
Late last year, as the pulsar headed toward its massive companion, the Large Area Telescope (LAT) aboard Fermi discovered faint gamma-ray emission.
"During the first disk passage, which lasted from mid-November to mid-December, the LAT recorded faint yet detectable emission from the binary. We assumed that the second passage would be similar, but in mid-January 2011, as the pulsar began its second passage through the disk, we started seeing surprising flares that were many times stronger than those we saw before," Abdo said.
Stranger still, the system's output at radio and X-ray energies showed nothing unusual as the gamma-ray flares raged.
"The most intense days of the flare were Jan. 20 and 21 and Feb. 2, 2011," said Abdo. "What really surprised us is that on any of these days, the source was more than 15 times brighter than it was during the entire month-and-a-half-long first passage."
The study will appear in the July 20 issue of The Astrophysical Journal Letters and is available online.
"One great advantage of the Fermi LAT observations is the continuous monitoring of the source, which gives us the most complete gamma-ray observations of this system," said Julie McEnery, the Fermi project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md.
Astronomers are continuing to analyze their bounty of data and working to understand the surprising flares. And in May 2014, when the pulsar once again approaches its giant companion, they'll be watching.
03/07/2011 - Clocking Neptune's spin
By tracking atmospheric features on Neptune, a University of Arizona scientist has accurately determined the planet’s rotation, a feat that had not been previously achieved for any of the gas planets in our solar system except Jupiter.
A day on Neptune lasts precisely 15 hours, 57 minutes, and 59 seconds, according to the first accurate measurement of its rotational period made by Erich Karkoschka from University of Arizona, Tucson.
His result is one of the largest improvements in determining the rotational period of a gas planet in almost 350 years since Italian astronomer Giovanni Cassini made the first observations of Jupiter’s Red Spot.
“The rotational period of a planet is one of its fundamental properties,” said Karkoschka. “Neptune has two features observable with the Hubble Space Telescope that seem to track the interior rotation of the planet. Nothing similar has been seen before on any of the four giant planets.”
Unlike the rocky planets — Mercury, Venus, Earth, and Mars — which behave like solid balls spinning in a rather straightforward manner, the giant gas planets — Jupiter, Saturn, Uranus and Neptune — rotate more like giant blobs of liquid. Because they are believed to consist of mainly ice and gas around a relatively small solid core, their rotation involves a lot of sloshing, swirling, and roiling, which has made it difficult for astronomers to get an accurate grip on exactly how fast they spin around.
“If you looked at Earth from space, you’d see mountains and other features on the ground rotating with great regularity, but if you looked at the clouds, they wouldn’t because the winds change all the time,” Karkoschka said. “If you look at the giant planets, you don’t see a surface, just a thick cloudy atmosphere.”
“On Neptune, all you see is moving clouds and features in the planet’s atmosphere. Some move faster, some move slower, some accelerate, but you really don’t know what the rotational period is, if there even is some solid inner core that is rotating.”
In the 1950s, when astronomers built the first radio telescopes, they discovered that Jupiter sends out pulsating radio beams, like a lighthouse in space. Those signals originate from a magnetic field generated by the rotation of the planet’s inner core.
No clues about the rotation of the other gas giants, however, were available because any radio signals they may emit are being swept out into space by the solar wind and never reach Earth.
“The only way to measure radio waves is to send spacecraft to those planets,” Karkoschka said. “When Voyager 1 and 2 flew past Saturn, they found radio signals and clocked them at exactly 10.66 hours, and they found radio signals for Uranus and Neptune, as well. So based on those radio signals, we thought we knew the rotation periods of those planets.”
But when the Cassini probe arrived at Saturn 15 years later, its sensors detected its radio period had changed by about 1 percent.
Karkoschka said that because of its large mass, it was impossible for Saturn to incur that much change in its rotation over such a short time.
“Because the gas planets are so big, they have enough angular momentum to keep them spinning at pretty much the same rate for billions of years,” he said. “So something strange was going on.”
Even more puzzling was Cassini’s later discovery that Saturn’s northern and southern hemispheres appear to be rotating at different speeds.
“That’s when we realized the magnetic field is not like clockwork but slipping,” Karkoschka said. “The interior is rotating and drags the magnetic field along, but because of the solar wind or other, unknown influences, the magnetic field cannot keep up with respect to the planet’s core and lags behind.”
Instead of spacecraft powered by billions of dollars, Karkoschka took advantage of what one might call the scraps of space science — publicly available images of Neptune from the Hubble Space Telescope archive. With determination and patience, he then pored over hundreds of images, recording every detail and tracking distinctive features over long periods of time.
Other scientists before him had observed Neptune and analyzed images, but nobody had sleuthed through 500 of them.
“When I looked at the images, I found Neptune’s rotation to be faster than what Voyager observed,” Karkoschka said. “I think the accuracy of my data is about 1,000 times better than what we had based on the Voyager measurements — a huge improvement in determining the exact rotational period of Neptune, which hasn’t happened for any of the giant planets for the last 3 centuries.”
Two features in Neptune’s atmosphere, Karkoschka discovered, stand out in that they rotate about 5 times more steadily than even Saturn’s hexagon, the most regularly rotating feature known on any of the gas giants.
Named the South Polar Feature and the South Polar Wave, the features are likely vortices swirling in the atmosphere, similar to Jupiter’s famous Red Spot, which can last for a long time due to negligible friction. Karkoschka was able to track them over the course of more than 20 years.
An observer watching the massive planet turn from a fixed spot in space would see both features appear exactly every 15.9663 hours, with less than a few seconds of variation.
“The regularity suggests those features are connected to Neptune’s interior in some way,” Karkoschka said. “How they are connected is up to speculation.”
One possible scenario involves convection driven by warmer and cooler areas within the planet’s thick atmosphere, analogous to hot spots within the Earth’s mantle, giant circular flows of molten material that stay in the same location over millions of years.
“I thought the extraordinary regularity of Neptune’s rotation indicated by the two features was something really special,”
Karkoschka said.
“So I dug up the images of Neptune that Voyager took in 1989, which have better resolution than the Hubble images, to see whether I could find anything else in the vicinity of those two features. I discovered six more features that rotate with the same speed, but they were too faint to be visible with the Hubble Space Telescope, and visible to Voyager only for a few months, so we wouldn’t know if the rotational period was accurate to the six digits. But they were really connected. So now we have eight features that are locked together on one planet, and that is really exciting.”
In addition to getting a better grip on Neptune’s rotational period, the study could lead to a better understanding of the giant gas planets in general.
“We know Neptune’s total mass but we don’t know how it is distributed,” Karkoschka said. “If the planet rotates faster than we thought, it means the mass has to be closer to the center than we thought. These results might change the models of the planets’ interior and could have many other implications.”
03/07/2011 - Astronomers reveal a cosmic "Axis of Evil"
The Coma Cluster is a massive cluster of galaxies in the local universe.
Astronomers are puzzled by the announcement that the masses of the largest objects in the universe appear to depend on which method is used to weigh them. The new work was presented at a specialist discussion meeting on “Scaling Relations of Galaxy Clusters” organized by the Astrophysics Research Institute (ARI) at Liverpool John Moores University and supported by the Royal Astronomical Society.
Clusters of galaxies are the largest gravitationally bound objects in the universe, containing thousands of galaxies like the Milky Way, and their weight is an important probe of their dark matter content and evolution through cosmic time. Measurements used to weigh these systems carried out in three different regions of the electromagnetic spectrum — X-ray, optical, and millimeter wavelengths — give rise to significantly different results.
Eduardo Rozo from the University of Chicago explained that any two of the measurements can be made to fit easily enough but that always leaves the estimate using the third technique out of line. Dubbed the “Axis of Evil,” it is as if the universe is being difficult by keeping back one or two pieces of the jigsaw and deliberately preventing researchers from calibrating our weighing scales properly.
More than 40 of the leading cluster astronomers from the United Kingdom, Europe, and the United States attended the meeting to discuss the early results from the Planck satellite, currently scanning the heavens at millimeter wavelengths, looking for the smallest signals from clusters of galaxies and the cosmic background radiation in order to understand the birth of the universe. The Planck measurements were compared with optical images of clusters from the Sloan Digitized Sky Survey and new X-ray observations from the XMM-Newton satellite.
ARI astronomers are taking a leading role in this research through participation in the X-ray cluster work and observations of the constituent galaxies using the largest ground-based optical telescopes.
One possible resolution to the “Axis of Evil” problem discussed at the meeting is a new population of clusters that is optically bright but also X-ray faint. Jim Bartlett from the University of Paris, who is one of the astronomers who presented the Planck results, argued that the prospect of a new cluster population that responds differently was a “frightening prospect” because it overturns age-old ideas about the gravitational physics being the same from cluster to cluster.
“I saw this meeting as an opportunity to bring together experts who study clusters at only one wavelength and don’t always talk to their colleagues working at other wavelengths,” said Chris Collins from ARI. “The results presented are unexpected, and all three communities — optical, X-ray, and millimeter — will need to work together in the future to figure out what is going on.”
03/07/2011 - Mars missions in summer slow lane
The 2016 orbiter would look for trace gases in the atmosphere of Mars
US and European efforts to send joint missions to Mars will stay in the slow lane over the summer while the Americans organise their finances.
European nations were hoping this week to release industry to start work on building an orbiter to hunt for methane in Mars' atmosphere in 2016.
But the full authority could not be given because Washington said it was not yet in a position to commit to the programme in its entirety, which includes sending a rover to the Red Planet two years later.
Faced with the Americans' uncertainty, European Space Agency member states decided not to issue an industrial contract to build the orbiter.
Instead, Esa will discuss with space companies what minimum works can be done on the project under existing arrangements to keep it on track - in the expectation that the US will come back with a proper commitment in September.
"It has been decided to take the minimum conservative measures to ensure no irreversible path is taken, and that those measures are taken within the existing contractual frame we have with the industry," said Eric Morel de Westgaver, the Paris-based agency's director for procurement.
The delay will be a worry for all concerned. Industry says the timetable for construction for the joint missions, particularly for the orbiter, is tight if launch dates are to be met; and that it cannot wait much longer to start fabrication of key components.
"We are already compressing the uncompressible", was how one industry official described the situation to the BBC at last week's Paris Air Show.
And at the same event, Jean-Jacques Dordain, Esa's director general, acknowledged the programme did not have "months of margin".
Known in Europe as the ExoMars project, the joint venture between the agencies comprises two separate, but related, missions.
The first, to launch in 2016, is a satellite that would track down the sources of methane and other trace gases recently detected in Mars' atmosphere.
The presence of methane is intriguing because its likely origin is either present-day life or geological activity. Confirmation of either would be a major discovery.
Then, in 2018, the agencies plan to send a single large rover to the Red Planet - perhaps targeted at one of the most interesting sources of methane to investigate it further. It would drill below the surface, and look for signs of life on the planet. The rover may even cache rocks for return to Earth by a later mission.
The 2016 satellite would probably act as the surface vehicle's data-relay station to get its pictures and other information back to scientists.
The missions were a key topic for discussion this week at a meeting of the European agency's Industrial Policy Committee (IPC) - its "cheque writing" body.
It was expected that the IPC would be presented with a letter from Nasa Administrator Charles Bolden explicitly affirming his country's commitment to take part in the rover mission in 2018.
A letter from Washington did arrive, but not until after the start of the two-day gathering. And in the letter, Mr Bolden said Nasa was not yet in a position to promise to provide a rocket, an interplanetary cruise stage to take the 2018 rover to Mars, and a landing system to put it on the surface.
These were all elements the Americans said they would like to contribute when the idea of joint missions was first established.
In the eyes of Esa, the 2016 orbiter and the 2018 rover are one programme, and without a firm undertaking from the Americans on the latter part of the venture, the Europeans are reluctant to press ahead on the former part.
"Before we embark on spending a lot of taxpayers' money, we want to be sure we have the commitment of Nasa," Mr Morel de Westgaver told BBC News.
Mr Bolden did say in his letter that he would be working within the US government to get that commitment, and that he hoped to be able to deliver it to the IPC before it meets again in September.
For followers of European space affairs, the ExoMars initiative has been a long, drawn-out affair. It was originally approved as a concept by ministers in 2005, but then went through several iterations as scientists and engineers struggled to match their ambitions for the project to the funds available.
A decision to combine efforts with the Americans was taken when they too encountered budget pressures on their Mars Programme.
03/07/2011 - Antimatter Tevatron mystery gains ground
The Dzero team is also part of a mystery about a potential new particle
US particle physicists are inching closer to determining why the Universe exists in its current form, made overwhelmingly of matter.
Physics suggests equal amounts of matter and antimatter should have been made in the Big Bang.
In 2010, researchers at the Tevatron accelerator claimed preliminary results showing a small excess of matter over antimatter as particles decayed.
The team has submitted a paper showing those results are on a firmer footing.
Each of the fundamental particles known has an antimatter cousin, with identical properties but opposite electric charge.
When a particle encounters its antiparticle, they "annihilate" each other, disappearing in a high-energy flash of light.
The question remains: why did this not occur in the early Universe with the equal amounts of matter and antimatter, resulting in a Universe devoid of both?
New physics?The Tevatron results come from a shower of particles produced at the facility when smashing protons into their antimatter counterparts, antiprotons.
The proton-antiproton collisions in turn create a number of different particles, and the team operating the Tevatron's DZero detector first noticed a discrepancy in the decay of particles called B mesons.
Statistics of a 'discovery'
- Particle physics has an accepted definition for a "discovery": a five-sigma level of certainty
- The number of sigmas is a measure of how unlikely it is that an experimental result is simply down to chance rather than a real effect
- Similarly, tossing a coin and getting a number of heads in a row may just be chance, rather than a sign of a "loaded" coin
- The "three sigma" level represents about the same likelihood of tossing more than eight heads in a row
- Five sigma, on the other hand, would correspond to tossing more than 20 in a row
- A five-sigma result is highly unlikely to happen by chance, and thus an experimental result becomes an accepted discovery
However, unpicking important events in the soup of interactions created in particle physics experiments meant that those measurements were associated with a level of uncertainty - reflecting the probability that the effect they see is a random statistical occurrence, rather than new physics.
The researchers now have 50% more data to work with, and have tried to establish that their earlier result in fact came from the particle decays that they first proposed.
As they reported this Thursday, they have now reduced the uncertainty in their experiment to a level of 3.9 sigma - equivalent to a 0.005% probability that the effect is a fluke.
But particle physics has a strict definition for what may be called a discovery - the "five sigma" level of certainty, or about a 0.00003% chance that the effect is not real - which the team must show before they can claim to have solved the long-standing matter/antimatter mystery.
29/06/2011 - Neutron star bites off more than it can chew
The European Space Agency’s (ESA) XMM-Newton space observatory has watched a faint star flare up at X-ray wavelengths to almost 10,000 times its normal brightness. Astronomers believe the outburst was caused by the star trying to eat a giant clump of matter.
The flare took place on a neutron star, the collapsed heart of a once much larger star. Now about 6 miles (10 kilometers) in diameter, the neutron star is so dense that it generates a strong gravitational field.
The clump of matter was much larger than the neutron star and came from its enormous blue supergiant companion star.
“This was a huge bullet of gas that the star shot out, and it hit the neutron star allowing us to see it,” said Enrico Bozzo from University of Geneva, Switzerland.
The flare lasted 4 hours and the X-rays came from the gas in the clump as it was heated to millions of degrees while being pulled into the neutron star’s intense gravity field. In fact, the clump was so big that not much of it hit the neutron star. Yet, if the neutron star had not been in its path, this clump would probably have disappeared into space without a trace.
XMM-Newton caught the flare during a scheduled 12.5-hour observation of the system, which is known only by its catalog number IGR J18410-0535, but the astronomers were unaware of their catch.
The telescope works through a sequence of observations carefully planned to make the best use of the space observatory’s time, then sends the data to Earth.
It was about 10 days after the observation that Bozzo and his colleagues received the data and quickly realized they had something special. Not only were they pointing in the right direction to see the flare, but also the observation had lasted long enough for them to see it from beginning to end.
“I don’t know if there is any way to measure luck, but we were extremely lucky,” said Bozzo. He estimates that an X-ray flare of this magnitude can be expected a few times a year at the most for this particular star system.
The duration of the flare allowed them to estimate the size of the clump. It was much larger than the star, probably 10 million miles (16 million km) across, or about 100 billion times the volume of the Moon. Yet, according to the estimate made from the flare’s brightness, the clump contained only one-thousandth of our natural satellite’s mass.
These figures will help astronomers understand the behavior of the blue supergiant and the way it emits matter into space. All stars expel atoms into space, creating a stellar wind. The X-ray flare shows that this particular blue supergiant does it in a clumpy fashion, and the estimated size and mass of the cloud allow constraints to be placed on the process.
“This remarkable result highlights XMM-Newton’s unique capabilities,” comments Norbert Schartel, XMM-Newton Project Scientist. “Its observations indicate that these flares can be linked to the neutron star attempting to ingest a giant clump of matter.”
29/06/2011 - China and UK strike space deal
Chinese and UK companies have agreed a deal that will result in three high-resolution Earth observation spacecraft being built to map China's extraordinary growth from orbit.
The deal was penned between Guildford satellite imagery provider DMCii and Beijing-based company 21AT.
It means DMCii can now roll out its new constellation of spacecraft that will picture details on the surface of the planet less than a metre wide.
They should be ready to launch in 2014.
For 21AT (Twenty First Century Aerospace Technology Company Ltd), it means it can have ready access to Earth imagery without the worry of having to launch and operate satellites in orbit.
The Chinese company will use the pictures to monitor land use and land-cover changes. In particular, the data will enable regional governments working with 21AT to plan better the extraordinary rate of development in China's cities.
The satellites for the DMC-3 constellation, as it is called, will be manufactured by DMCii's parent company, Surrey Satellite Technology Limited (SSTL).
29/06/2011 - A Glitch in Pulsar J1718-3718
Pulsars are noted as being some of the universe’s best clocks. Their highly magnetized nature gives rise to beams of high energy radiation that sweep out across the universe. If these beams pass Earth, they can rival atomic clocks in their precision. So precise are these timings, that the first extrasolar planet was discovered through the effects it had on this heartbeat. But in September of 2007, pulsar J1718-3719 appears to have had a seizure.
These disjunctions aren’t unprecedented. While not exactly frequent, such “glitches” have been noted previously in other pulsars and magnetars. These glitches are often displayed as a sudden change in the period of the pulsar suddenly drops and then slowly relaxes back to the pre-glitch value at a characteristic rate dependent on the previous value as well as how large the jump was. Behavior like this has been seen in other pulsars including PSR B2334+61 and PSR 1048-5397.
The size of a glitch is measured as a ratio of the change in speed due to the glitch as compared to that of the pre-glitch speed. For past glitches, these have generally been changes that are around a hundredth of a percent. While this may not sound like a large change, the stars on which they act are exceptionally dense neutron stars. As such, even a small change in rotational energy means a large amount of energy involved.
Previously, the largest known glitch was 20.5 x 10-6 for PSR B2334+61. The new glitch in PSR J1718-3718 beats this record with a frequency change of 33.25 x 10-6. Aside from being a record setter, this new glitch does not appear to be following the trend of returning to previous values. The changed period persisted for the 700 days astronomers at the Australia Telescope National Facility observed it. Pulsars tend to have a slow braking applied to them due to a difference between their rotational axes and their magnetic ones. This too generally returns to a standard value for a given pulsar following a glitch, but PSR J1718-3718 defied expectations here as well, having a persistently higher braking effect which has continued to increase.
Currently, astronomers know precious little about the effects which may cause these glitches. There is no evidence to suggest that the phenomenon is something external to the body itself. Instead, astronomers suspect that there are occasional alignments of the stars internal superfluid core which rotates more quickly, with the star’s crust that cause the two to occasionally lock together. Models of neutron stars have had some success at reproducing this odd behavior, but none have suggested an event like PSR J1718-3718. Instead, the authors of the recent study suggest that this may have been caused by a fracturing of the crust of the neutron star or some yet unknown internal reaction. The possibilities currently are not well constrained but studying future events like these will help astronomers refine their models.
29/06/2011 - 3D Galaxies – Coming Straight On For You
As we’ve recently learned, the ATLAS3D project was able to study 260 individual galaxies and do some very amazing things. By imaging in both red and blue shift, astronomers were able to take stellar measurements and give us a clear picture of galaxy rotation. But looking at a computer generated image gives a picture just like you reading the text in this article – no dimension. By superimposing the velocity of the stars over the plane of the image, a new breakthrough in simulation can be made. And it’s coming straight on for you…
We understand images of grand spirals and their sweeping arms. We marvel at photos of dust-lanes in those far off distant island universes. Even the motley elliptical galaxy gives us a sense of shape. But what would happen if we could take a different angle at what we see? How would galaxy mergers affect rotation? When galaxies collide, it sparks new starbirth… But how would it look?
“Young galaxies seem to have lots of gas that hasn’t yet been turned into burning stars — and they spin fast, so they look like the poster-child galaxy with spiral arms and dust lanes.” says the ATLAS team. “By telling us how fast stars in a galaxy rotate around their galaxy’s centre, the ATLAS3D result changes our understanding of galaxies and how they evolve over time.”
By studying these new images and techniques, astronomers will be able to tell us more about galaxies that have survived a crash and lived to spin. It could very well be that mergers of this type don’t affect orderly rotation and overall symmetry. The ATLAS3D team has already prepared computer simulations and performed more telescope observations to test this idea. And it’s coming straight on… Straight on for you.
We understand images of grand spirals and their sweeping arms. We marvel at photos of dust-lanes in those far off distant island universes. Even the motley elliptical galaxy gives us a sense of shape. But what would happen if we could take a different angle at what we see? How would galaxy mergers affect rotation? When galaxies collide, it sparks new starbirth… But how would it look?
“Young galaxies seem to have lots of gas that hasn’t yet been turned into burning stars — and they spin fast, so they look like the poster-child galaxy with spiral arms and dust lanes.” says the ATLAS team. “By telling us how fast stars in a galaxy rotate around their galaxy’s centre, the ATLAS3D result changes our understanding of galaxies and how they evolve over time.”
By studying these new images and techniques, astronomers will be able to tell us more about galaxies that have survived a crash and lived to spin. It could very well be that mergers of this type don’t affect orderly rotation and overall symmetry. The ATLAS3D team has already prepared computer simulations and performed more telescope observations to test this idea. And it’s coming straight on… Straight on for you.
28/06/2011 - Date set for final Shuttle Launch
The last launch of a US space shuttle will take place on Friday 8 July.
The Atlantis ship has the honour of closing out the 30-year orbiter programme and will lift off at 1126 Florida time (1526 GMT).
Up to 750,000 people are expected to line the roads and beaches around the Kennedy Space Center, all eager to witness a piece of history.
The launch date was fixed by US space agency managers on Tuesday following a review of mission preparations.
They passed as fit to fly a new fuel valve on one of the vehicle's main engines. The old valve was suspected to have a leak and was changed.
And inspections ordered on support beams on the ship's big orange external fuel tank found no issues of concern. Cracks in these structures were the cause of a major delay on a previous shuttle mission.
Four astronauts will ride Atlantis to orbit - Commander Chris Ferguson, Pilot Doug Hurley, and Mission Specialists Sandy Magnus and Rex Walheim.
Their 12-day sortie will take them to the International Space Station (ISS), where they will deliver more than 3.5 tonnes (8,000lb) of supplies - including a year's worth of food. It will give the US space agency some room to play with as it looks to introduce a commercial cargo re-supply service over the next 12 months.
"This flight is incredibly important to space station; the cargo that is coming up is really mandatory," said Nasa's Associate Administrator for Space Operations, Bill Gerstenmaier.
A shuttle would normally fly with six or seven crew members onboard, but the number has been reduced for this final flight because there is no orbiter left on standby to go and rescue them should they to get into trouble.
In the event of Atlantis sustaining serious damage on lift-off, similar to the ill-fated Columbia ship in 2003, the astronauts would take refuge on the ISS until they could all return to Earth in Russian Soyuz capsules over a 10-month period.
On its return from space, Atlantis will be put on public display at the Kennedy Space Center visitor complexThe 8 July ascent will be the 135th shuttle launch and the 33rd of Atlantis.
In total, 355 individuals will have flown 852 times on those 135 missions since the very first shuttle flight on 12 April, 1981.
The five orbiters used over the course of the programme have flown 864,401,200km (537,114,016 miles) - a distance roughly similar to travelling from the Earth to the Sun and back three times.
Atlantis will add a further 6.5 million km (four million miles) to that total.
Reflecting on the significance of a final shuttle mission, Commander Ferguson said recently: "I don't think that the full magnitude of the moment will really hit us until the wheels have stopped on the runway.
"I'm not sure words will really be able to capture for the crew and for the entire shuttle workforce just how much the shuttle programme has meant to us for the last 30 years."
It has been an emotional few months for everyone connected with the programme - not least because many shuttle workers have lost their jobs in the wind-down.
Discovery was the first ship to complete its career in March, followed by Endeavour which landed one last time on 1 June.
The vehicles are all being retired to museums. Atlantis will end its days at the Kennedy Space Center visitor complex.
28/06/2011 - Near miss for International Space Station
A piece of debris has narrowly missed the International Space Station (ISS), forcing its six crew members to go to their escape capsules and prepare for an emergency evacuation back to Earth.
Officials said the debris came within 335m (1,100ft) of the platform.
The crew were given the all clear to return to work minutes after the object passed by at 1208 GMT.
The junk was of unknown size but experts say even a small object could do considerbale damage to the ISS.
The US space agency's (Nasa) Associate Administrator for Space Operations, Bill Gerstenmaier, said it was the closest a debris object had ever come to the station. An analysis was now underway to try to understand its origin, he added.
"A situation arose linked to unidentified 'space trash' passing very close to the space station," the Russian space agency had earlier explained.
"The crew was told to take their places aboard the Soyuz spacecraft."
Soyuz capsules are used to ferry crew to and from the orbiting platform, and enough vehicles are always present so that they can be used as "lifeboats" if an emergency arises.
Before getting into the capsules, the crew closed all the hatches on the ISS.
The ISS is currently manned by three Russians, two Americans and a Japanese astronaut.
Dangerous fragmentsA Russian official said that only 10% of all objects in Earth's orbit are satellites, while the rest is rubbish: spent rocket stages, defunct satellites, acceleration blocks and other debris.
Scientists estimate that there are more than 300,000 junk fragments in space of up to 10cm (four inches) in length, but there are many millions more pieces that are smaller.
Even fragments a few centimetres in size are a hazard because they travel at many thousands of kilometres per hour.
Normally, the station can be moved out of the way of a piece of junk, but this alert was raised too late for such a manoeuvre.
Three crew members were forced briefly to evacuate the space station in an incident in March 2009.
The station is a $100bn project that has been under construction about 220m (350km) above the Earth since 1998. Five partners are involved - the US, Russia, Japan, Canada and Europe (10 nations coordinated through the European Space Agency).
26/06/2011 - Firestorm of Star Birth in the Active Galaxy Centaurus A
Resembling looming rain clouds on a stormy day, dark lanes of dust crisscross the giant elliptical galaxy Centaurus A. Hubble's panchromatic vision, stretching from ultraviolet through near-infrared wavelengths, reveals the vibrant glow of young, blue star clusters and a glimpse into regions normally obscured by the dust. This image was taken in July 2010 with Hubble's Wide Field Camera 3. (HubbleSite)
26/06/2011 - NASA's Hubble Finds Rare Blue Straggler Stars in the Milky Way's Hub
Probing the star-filled, ancient hub of our Milky Way, NASA's Hubble Space Telescope has found a rare class of oddball stars called blue stragglers, the first time such objects have been detected within our galaxy's bulge.
The size and nature of the blue straggler population detected in the bulge will allow astronomers to better understand if the bulge is exclusively old stars, or a mixture of both young and old stars. In addition, the discovery provides a new test case for formation models of the blue stragglers themselves.
Blue stragglers — so named because they seem to be lagging behind in their rate of aging compared with the population from which they formed — were first found inside ancient globular star clusters half a century ago. They have been detected in many globular and open clusters, as well as among the stars in the solar neighborhood. But they have never been seen inside the core of our galaxy until Hubble was trained on the region.
Hubble astronomers found blue straggler stars in an extensive set of Hubble exposures of the Milky Way's crowded hub. Blue stragglers are much hotter — and hence bluer — than they should be for the aging neighborhood in which they live. Now that blue stragglers have at last been found within the bulge, the size and characteristics of this population will allow astronomers to better understand the still-controversial processes of star formation within the bulge.
The results, to be published in The Astrophysical Journal, are being reported by lead author Will Clarkson of Indiana University and the University of California, Los Angeles, at the American Astronomical Society meeting in Boston, Mass.
These results support the idea that the Milky Way's central bulge stopped making stars billions of years ago. It is now home to aging Sun-like stars and cooler red dwarfs. Giant blue stars that once lived there exploded as supernovae billions of years ago. If our galaxy were the size of a dinner plate, the central bulge would be roughly the size of a grapefruit placed in the middle of the plate.
This discovery is a spin-off from a seven-day-long survey conducted in 2006 called the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS). Hubble peered at and obtained variability information for 180,000 stars in the crowded central bulge of our galaxy, 26,000 light-years away. The survey was intended to find hot Jupiter-class planets that orbit very close to their stars. But the SWEEPS team also uncovered 42 oddball blue stars among the bulge population with brightness and temperatures typical for stars much younger than ordinary bulge stars.
Blue stragglers have long been suspected to be living in the bulge. Until now, it has never been proven because younger stars in the disk of our galaxy lie along the line-of-sight to the core, confusing and contaminating the view.
But Hubble's view is so sharp that astronomers could distinguish the motion of the core population from foreground stars in the Milky Way. Bulge stars orbit the galactic nucleus at a different speed than foreground stars. Plotting their motion required returning to the SWEEPS target region with Hubble two years after the first-epoch observations were made.
Hence, the blue stragglers were identified as moving along with the other stars in the bulge. It's like looking into a deep, clear pond where the fish at the bottom of the pond are swimming at a faster rate than the fish closer to the surface.
"The size of the field of view on the sky is roughly that of the thickness of a human fingernail held at arm's length, and within this region, Hubble sees about a quarter million stars towards the bulge," Clarkson says. "Only the superb image quality and stability of Hubble allowed us to make this measurement in such a crowded field."
From the 42 candidate blue stragglers, the investigators estimate 18 to 37 of them are likely to be genuine blue stragglers, with the remainder consisting of a mixture of foreground objects and at most a small population of genuinely young bulge stars.
It's not clear how blue stragglers form, or if there is more than one mechanism at work. A common idea is that blue stragglers emerge from binary pairs. As the more massive star evolves and expands, the less massive star accretes material from the companion. This stirs up hydrogen fuel and causes the accreting star to undergo nuclear fusion at a faster rate. It burns hotter and bluer.
The seven-day observation allowed the fraction of blue straggler candidates presently in close binaries to be estimated by virtue of their changing light-curve. This is caused by the change of shape induced in one star due to the tidal gravitational pull of its companion. "The SWEEPS program was designed to detect transiting planets through small light variations. Therefore the program could easily detect the variability of binary pairs, which was crucial in confirming these are indeed blue stragglers," says Kailash Sahu of the Space Telescope Science Institute in Baltimore, Md., the principal investigator of the SWEEPS program.
The observations clearly indicate that if there is a young star population in the bulge, it is very small, and it was not detected in the SWEEPS program. "Although the Milky Way bulge is by far the closest galaxy bulge, several key aspects of its formation and subsequent evolution remain poorly understood," Clarkson says. "While the consensus is that the bulge largely stopped forming stars long ago, many details of its star-formation history remain controversial. The extent of the blue straggler population detected provides two new constraints for models of the star-formation history of the bulge." (HubbleSite)
26/06/2011 - Cosmology in the Year 1 Trillion
Much of what is known today about the birth of the cosmos comes from astronomical observations at high redshifts. Due to the accelerated expansion of the Universe, however, astronomers of the future will be unable to use the same methods. In a trillion years or so, our own Milky Way galaxy will have merged with the Andromeda galaxy, creating a new galaxy that has been quaintly termed “Milkomeda.” All of our other galactic neighbors will have long disappeared beyond our cosmological horizon. Even the CMB will have been stretched into invisibility. So how will future Milkomedans study cosmology? How will they figure out where the Universe came from?
According to a paper published by the Harvard-Smithsonan Center for Astrophysics, these astronomers will be able to decode the secrets of the cosmos by studying stellar runaways from their own galaxy: so-called hypervelocity stars (HVSs). HVSs originate in binary or triple-star systems that wander just a hair too close to their galaxy’s central supermassive black hole. Astronomers believe that one star from the system is captured by the black hole, while the others are sent careening out of the galaxy at colossally high speeds. HVS ejections occur relatively rarely (approximately once every 10,000-100,000 years) and should continue to occur for trillions of years, given the large density of stars in the galactic center.
So how would HVSs help future astronomers study the origins of the Universe? First, these scientists would have to locate an ejected star beyond the gravitational boundary of Milkomeda. Once beyond this boundary (after about 2 billion years of travel), the acceleration of a HVS could be attributed entirely to the Hubble flow. With advanced technology, future astronomers could use the Doppler shift of its spectral lines and thus deduce Einstein’s cosmological constant and the acceleration of the Universe at large. Next, scientists could use mathematical models of galaxy formation and collapse to determine the Universe’s mass density and age at the time that Milkomeda formed. From their knowledge of the galaxy’s age, they would be able to tell when the Big Bang occurred.