Posted on by Nancy Atkinson

Shapes Reveal Supernovae History

These two supernova remnants are part of a new study from NASA’s Chandra X-ray Observatory that shows how the shape of the remnant is connected to the way the progenitor star exploded. Credit: NASA/CXC/UCSC/L. Lopez et al.)

At a very early age, children learn how to classify objects according to their shape. Now, new research suggests studying the shape of the aftermath of supernovas may allow astronomers to do the same. Images of supernova remnants taken by the Chandra X-ray Observatory shows that the symmetry of the debris from exploded stars, or lack thereof, reveals how the star exploded. This is an important discovery because it shows that the remnants retain information about how the star exploded even though hundreds or thousands of years have passed.

“It’s almost like the supernova remnants have a ‘memory’ of the original explosion,” said Laura Lopez of the University of California at Santa Cruz, who led the study. “This is the first time anyone has systematically compared the shape of these remnants in X-rays in this way.”

Astronomers sort supernovas into several categories, or “types”, based on properties observed days after the explosion and which reflect very different physical mechanisms that cause stars to explode. But, since observed remnants of supernovas are leftover from explosions that occurred long ago, other methods are needed to accurately classify the original supernovas.

Lopez and colleagues focused on the relatively young supernova remnants that exhibited strong X-ray emission from silicon ejected by the explosion so as to rule out the effects of interstellar matter surrounding the explosion. Their analysis showed that the X-ray images of the ejecta can be used to identify the way the star exploded. The team studied 17 supernova remnants both in the Milky Way galaxy and a neighboring galaxy, the Large Magellanic Cloud.

Chandra X-ray Image of SNR 0548-70.4 (Credit: NASA/CXC/UCSC/L. Lopez et al.)
Chandra X-ray Image of SNR 0548-70.4 (Credit: NASA/CXC/UCSC/L. Lopez et al.)

For each of these remnants there is independent information about the type of supernova involved, based not on the shape of the remnant but, for example, on the elements observed in it. The researchers found that one type of supernova explosion – the so-called Type Ia – left behind relatively symmetric, circular remnants. This type of supernova is thought to be caused by a thermonuclear explosion of a white dwarf, and is often used by astronomers as “standard candles” for measuring cosmic distances.

On the other hand, the remnants tied to the “core-collapse” supernova explosions were distinctly more asymmetric. This type of supernova occurs when a very massive, young star collapses onto itself and then explodes.

“If we can link supernova remnants with the type of explosion”, said co-author Enrico Ramirez-Ruiz, also of University of California, Santa Cruz, “then we can use that information in theoretical models to really help us nail down the details of how the supernovas went off.”

Models of core-collapse supernovas must include a way to reproduce the asymmetries measured in this work and models of Type Ia supernovas must produce the symmetric, circular remnants that have been observed.

Out of the 17 supernova remnants sampled, ten were classified as the core-collapse variety, while the remaining seven of them were classified as Type Ia. One of these, a remnant known as SNR 0548-70.4, was a bit of an “oddball”. This one was considered a Type Ia based on its chemical abundances, but Lopez finds it has the asymmetry of a core-collapse remnant.

“We do have one mysterious object, but we think that is probably a Type Ia with an unusual orientation to our line of sight,” said Lopez. “But we’ll definitely be looking at that one again.”

While the supernova remnants in the Lopez sample were taken from the Milky Way and its close neighbor, it is possible this technique could be extended to remnants at even greater distances. For example, large, bright supernova remnants in the galaxy M33 could be included in future studies to determine the types of supernova that generated them.

The paper describing these results appeared in the November 20 issue of The Astrophysical Journal Letters.

Source: Chandra

Posted on by Nancy Atkinson

Galaxy Cluster Far, Far Away Smashes Distance Record

JKC041 galaxy cluster. Credit: X-ray: NASA/CXC/INAF/S.Andreon et al Optical: DSS; ESO/VLT

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A galaxy cluster located about 10.2 billion light years from Earth has been discovered by combining data from NASA’s Chandra X-ray Observatory with optical and infrared telescopes. The cluster, JKCS041, is the most distant galaxy cluster yet observed, and we see it as when the Universe was only about a quarter of its present age. The cluster’s distance beats the previous record holder by about a billion light years.

Galaxy clusters are the largest gravitationally bound objects in the Universe. Finding such a large structure at this very early epoch can reveal important information about how the Universe evolved at this crucial stage.

JKCS041 is at the brink of when scientists think galaxy clusters can exist in the early Universe based on how long it should take for them to assemble. Therefore, studying its characteristics – such as composition, mass, and temperature – will reveal more about how the Universe took shape.

“This object is close to the distance limit expected for a galaxy cluster,” said Stefano Andreon of the National Institute for Astrophysics (INAF) in Milan, Italy. “We don’t think gravity can work fast enough to make galaxy clusters much earlier.”

JKCS041 was originally detected in 2006 in a survey from the United Kingdom Infrared Telescope (UKIRT). The distance to the cluster was then determined from optical and infrared observations from UKIRT, the Canada-France-Hawaii telescope in Hawaii and NASA’s Spitzer Space Telescope. Infrared observations are important because the optical light from the galaxies at large distances is shifted into infrared wavelengths because of the expansion of the universe.

The Chandra data were the final – but crucial – piece of evidence as they showed that JKCS041 was, indeed, a genuine galaxy cluster. The extended X-ray emission seen by Chandra shows that hot gas has been detected between the galaxies, as expected for a true galaxy cluster rather than one that has been caught in the act of forming.

Also, without the X-ray observations, the possibility remained that this object could have been a blend of different groups of galaxies along the line of sight, or a filament, a long stream of galaxies and gas, viewed front on. The mass and temperature of the hot gas detected estimated from the Chandra observations rule out both of those alternatives.

The extent and shape of the X-ray emission, along with the lack of a central radio source argue against the possibility that the X-ray emission is caused by scattering of cosmic microwave background light by particles emitting radio waves.

It is not yet possible, with the detection of just one extremely distant galaxy cluster, to test cosmological models, but searches are underway to find other galaxy clusters at extreme distances.

“This discovery is exciting because it is like finding a Tyrannosaurus Rex fossil that is much older than any other known,” said co-author Ben Maughan, from the University of Bristol in the United Kingdom. “One fossil might just fit in with our understanding of dinosaurs, but if you found many more, you would have to start rethinking how dinosaurs evolved. The same is true for galaxy clusters and our understanding of cosmology.”

The previous record holder for a galaxy cluster was 9.2 billion light years away, XMMXCS J2215.9-1738, discovered by ESA’s XMM-Newton in 2006. This broke the previous distance record by only about 0.1 billion light years, while JKCS041 surpasses XMMXCS J2215.9 by about ten times that.

“What’s exciting about this discovery is the astrophysics that can be done with detailed follow-up studies,” said Andreon.

Among the questions scientists hope to address by further studying JKCS041 are: What is the build-up of elements (such as iron) like in such a young object? Are there signs that the cluster is still forming? Do the temperature and X-ray brightness of such a distant cluster relate to its mass in the same simple way as they do for nearby clusters?

Source: EurekAlert

Posted on by Nancy Atkinson

New Chandra Deep X-ray Image of the Galactic Center

•A deep new image of the center of the Milky Way by the Chandra X-ray Observatory. NASA/CXC/UMass/D. Wang et al.

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Chandra has done it again in creating some of the most visually stunning images of our Universe. This time, Chandra’s X-ray eyes show a dramatic new vista of the center of the Milky Way galaxy. This mosaic from 88 different images exposes new levels of the complexity and intrigue in the Galactic center, providing a look at stellar evolution, from bright young stars to black holes, in a crowded, hostile environment dominated by a central, supermassive black hole.

Permeating the region is a diffuse haze of X-ray light from gas that has been heated to millions of degrees by winds from massive young stars – which appear to form more frequently here than elsewhere in the Galaxy – explosions of dying stars, and outflows powered by the supermassive black hole – known as Sagittarius A* (Sgr A*). Data from Chandra and other X-ray telescopes suggest that giant X-ray flares from this black hole occurred about 50 and about 300 years earlier.

See this link for an animation that provides greater detail of the galactic center.

The area around Sgr A* also contains several mysterious X-ray filaments. Some of these likely represent huge magnetic structures interacting with streams of very energetic electrons produced by rapidly spinning neutron stars or perhaps by a gigantic analog of a solar flare.

Scattered throughout the region are thousands of point-like X-ray sources. These are produced by normal stars feeding material onto the compact, dense remains of stars that have reached the end of their evolutionary trail – white dwarfs, neutron stars and black holes.

Because X-rays penetrate the gas and dust that blocks optical light coming from the center of the galaxy, Chandra is a powerful tool for studying the Galactic Center. This image combines low energy X-rays (colored red), intermediate energy X-rays (green) and high energy X-rays (blue).

The image is being released at the beginning of the “Chandra’s First Decade of Discovery” symposium being held in Boston, Mass. This four-day conference will celebrate the great science Chandra has uncovered in its first ten years of operations. To help commemorate this event, several of the astronauts who were onboard the Space Shuttle Columbia – including Commander Eileen Collins – that launched Chandra on July 23, 1999, will be in attendance.

Source: Chandra

Posted on by Nancy Atkinson

After Loss of Lunar Orbiter, India Looks to Mars Mission

India Moon Mission
Artist concept of Chandrayaan-1 orbiting the moon. Credit: ISRO

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After giving up on re-establishing contact with the Chandrayaan-1 lunar orbiter, Indian Space Research Organization (ISRO) Chairman G. Madhavan Nair announced the space agency hopes to launch its first mission to Mars sometime between 2013 and 2015. Nair said the termination of Chandrayaan-1, although sad, is not a setback and India will move ahead with its plans for the Chandrayaan-2 mission to land an unmanned rover on the moon’s surface to prospect for chemicals, and in four to six years launch a robotic mission to Mars.


“We have given a call for proposal to different scientific communities,” Nair told reporters. “Depending on the type of experiments they propose, we will be able to plan the mission. The mission is at conceptual stage and will be taken up after Chandrayaan-2.”

On the decision to quickly pull the plug on Chandrayaan-1, Nair said, “There was no possibility of retrieving it. (But) it was a great success. We could collect a large volume of data, including more than 70,000 images of the moon. In that sense, 95 percent of the objective was completed.”

Contact with Chandrayaan-1 may have been lost because its antenna rotated out of direct contact with Earth, ISRO officials said. Earlier this year, the spacecraft lost both its primary and back-up star sensors, which use the positions of stars to orient the spacecraft.

The loss of Chandrayaan-1 comes less than a week after the spacecraft’s orbit was adjusted to team up with NASA’s Lunar Reconnaissance Orbiter for a Bi-static radar experiment. During the maneuver, Chandrayaan-1 fired its radar beam into Erlanger Crater on the moon’s north pole. Both spacecraft listened for echoes that might indicate the presence of water ice – a precious resource for future lunar explorers. The results of that experiment have not yet been released.

Chandrayaan-1 craft was designed to orbit the moon for two years, but lasted 315 days. It will take about 1,000 days until it crashes to the lunar surface and is being tracked by the U.S. and Russia, ISRO said.

The Chandrayaan I had 11 payloads, including a terrain-mapping camera designed to create a three-dimensional atlas of the moon. It is also carrying mapping instruments for the European Space Agency, radiation-measuring equipment for the Bulgarian Academy of Sciences and two devices for NASA, including the radar instrument to assess mineral composition and look for ice deposits. India launched its first rocket in 1963 and first satellite in 1975. The country’s satellite program is one of the largest communication systems in the world.

Sources: New Scientist, Xinhuanet

Posted on by Nancy Atkinson

LRO, Chandrayaan-1 Team Up For Unique Search for Water Ice

Chandrayaan-1, India’s first unmanned mission to the Moon, successfully entered lunar orbit on November 8, 2008

NASA’s Lunar Reconnaissance Orbiter and India’s Chandrayaan-1 will team up on August 20 to perform a Bi-Static radar experiment to search for water ice in a crater on the Moon’s north pole. Both spacecraft will be in close proximity approximately 200 km above the lunar surface, and both are equipped with radar instruments. The two instruments will look at the same location from different angles, with Chandrayaan-1’s radar transmitting a signal which will be reflected off the interior of Erlanger crater, and then be picked up by LRO. Scientists will compare the signal that bounces straight back to Chandrayaan with the signal that bounces at a slight angle to LRO to garner unique information, particularly about any water ice that may be present inside the crater.

Both spacecraft are equipped with a NASA Miniature Radio Frequency (RF) instrument that functions as a Synthetic Aperture Radar (SAR), known as Mini-SAR on Chandrayaan 1 and Mini-RF on LRO.

“The advantage of a Bi-Static experiment is that you’re looking at echoes that are being reflected off the Moon at an angle other than zero,” said Paul Spudis,principal investigator for Chandrayaan-1’s Mini-SAR,discussing the mission on The Space Show. “Mono-static radar sends a pulse, and you are looking in the same phase or incident angle. But with Bi-Static, you can look at it from a different angle. The significance of that is ice has a very unique bi-static response.”

Erlanger Crater from the Lunar Orbiter. Credit: NASA
Erlanger Crater from the Lunar Orbiter. Credit: NASA

Stewart Nozette, Mini-RF principal investigator from the Universities Space Research Association’s Lunar and Planetary Institute, said, “An extraordinary effort was made by the whole NASA team working with ISRO to make this happen”

While this coordination sounds easy, this experiment is extremely challenging because both spacecraft are traveling at about 1.6 km per second and will be looking at an area on the ground about 18 km across. Due to the extreme speeds and the small point of interest, NASA and ISRO need to obtain and share information about the location and pointing of both spacecraft. The Bi-Static experiment requires extensive tracking by ground stations of NASA’s Deep Space Network, the Applied Physics Laboratory, and ISRO.

Even with the considerable planning and coordination between the U.S. and India the two instrument beams may not overlap, or may miss the desired location. Even without hitting the exact location Scientists may still be able to use the Bi-Static information to further knowledge already received from both instruments.

“The international coordination and cooperation between the two agencies for this experiment is an excellent opportunity to demonstrate future cooperation between NASA and ISRO, “says Jason Crusan, program executive for the Mini-RF program, from NASA’s Space Operations Mission Directorate, Washington, D.C.

Posted on by Nancy Atkinson

Trigger-Happy Star Formation in Cepheus B

Cepheus B from Chandra and Spitzer: X-ray (NASA/CXC/PSU/K. Getman et al.); IR (NASA/JPL-Caltech/CfA/J. Wang et al.)

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Combining data from the Chandra X-Ray Observatory and the Spitizer Space Telescope allowed astronomers to create this gorgeous new image of Cepheus B. Besides being incredible eye candy, the new image also provides fresh insight into how some stars are born. The research shows that radiation from massive stars may trigger the formation of many more stars than previously thought.

While astronomers have long understood that stars and planets form from the collapse of a cloud of gas, the question of the main causes of this process has remained open.

“Astronomers have generally believed that it’s somewhat rare for stars and planets to be triggered into formation by radiation from massive stars,” said Konstantin Getman of Penn State University, and lead author of the study. “Our new result shows this belief is likely to be wrong.”

Chandra image of Cepheus B. Credit: NASA/Chandra team
Chandra image of Cepheus B. Credit: NASA/Chandra team

The new study suggests that star formation in the region of study in this image, Cepheus B, is mainly triggered by radiation from one bright, massive star outside the molecular cloud. According to theoretical models, radiation from this star would drive a compression wave into the cloud triggering star formation in the interior, while evaporating the cloud’s outer layers. The Chandra-Spitzer analysis revealed slightly older stars outside the cloud while the youngest stars with the most protoplanetary disks congregate in the cloud interior — exactly what is predicted from the triggered star formation scenario.

“We essentially see a wave of star and planet formation that is rippling through this cloud,” said co-author Eric Feigelson, also of Penn State. “Outside the cloud, the stars probably have newly born planets while inside the cloud the planets are still gestating.”

Cepheus B is a cloud of mainly cool molecular hydrogen located about 2,400 light years from the Earth. There are hundreds of very young stars inside and around the cloud — ranging from a few millions years old outside the cloud to less than a million in the interior — making it an important testing ground for star formation.

Previous observations of Cepheus B had shown a rim of ionized gas around the molecular cloud and facing the massive star. However, the wave of star formation — an additional crucial feature to identifying the source of the star formation — had not previously been seen. “We can even clock how quickly this wave is traveling and it’s going about 2,000 miles per hour,” said Getman.

The star that is the catalyst for the star formation in Cepheus B, is about 20 times as massive as the Sun, or at least five times weightier than any of the other stars in Cepheus B.

The Chandra and Spitzer data also suggest that multiple episodes of star and planet formation have occurred in Cepheus B over millions of years and that most of the material in the cloud has likely already been evaporated or transformed into stars.

“It seems like this nearby cloud has already made most of its stars and its fertility will soon wane,” said Feigelson. “It’s clear that we can learn a lot about stellar nurseries by combining data from these two Great Observatories.”

A paper describing these results was published in the July 10 issue of the Astrophysical Journal.

Source: Chandra

Posted on by Fraser Cain

Milky Way’s Black Hole Gave Off a Burst 300 Years Ago

Sagittarius A*. Image credit: Chandra

Our Milky Way’s black hole is quiet – too quiet – some astronomers might say. But according to a team of Japanese astronomers, the supermassive black hole at the heart of our galaxy might be just as active as those in other galaxies, it’s just taking a little break. Their evidence? The echoes from a massive outburst that occurred 300 years ago.

The astronomers found evidence of the outburst using ESA’s XMM-Newton space telescope, as well as NASA and Japanese X-ray satellites. And it helps solve the mystery about why the Milky Way’s black hole is so quiet. Even though it contains 4 million times the mass of our Sun, it emits a fraction of the radiation coming from other galactic black holes.

“We have wondered why the Milky Way’s black hole appears to be a slumbering giant,” says team leader Tatsuya Inui of Kyoto University in Japan. “But now we realize that the black hole was far more active in the past. Perhaps it’s just resting after a major outburst.”

The team gathered their observations from 1994 to 2005. They watched how clouds of gas near the central black hole brightened and dimmed in X-ray light as pulses of radiation swept past. These are echoes, visible long after the black hole has gone quiet again.

One large gas cloud is known as Sagittarius B2, and it’s located 300 light-years away from the central black hole. In other words, radiation reflecting off of Sagittarius B2 must have come from the black hole 300 years previously.

By watching the region for more than 10 years, the astronomers were able to watch an event wash across the cloud. Approximately 300 years ago, the black hole unleashed a flare that made it a million times brighter than it is today.

It’s hard to explain how the black hole could vary in its radiation output so greatly. It’s possible that a supernova in the region plowed gas and dust into the vicinity of the black hole. This led to a temporary feeding frenzy that awoke the black hole and produced the great flare.

Original Source: ESA News Release

Posted on by Nancy Atkinson

New Chandra Image Is Eye Candy

This picture is too gorgeous not to share it. A new Chandra X-ray telescope image shows a beautiful, dense region of massive stars in the Centaurus constellation. It almost appears as though someone threw a handful of colored candies out into space. Known as Westerlund 2, this star cluster has been a mysterious region of our galaxy, filled with dust and gas that have obscured our vision of what lies inside. But new X-ray observations with Chandra have revealed some of the hottest, brightest and most massive known stars, and this is now regarded as one of the most interesting star clusters in the Milky Way galaxy.

About 20,000 light years from Earth, Westerlund 2 is a young star cluster with an estimated age of about one or two million years. An extremely massive double star system called WR20a is visible in the image, the bright yellow point just below and to the right of the cluster’s center. This system contains stars with whopping masses of 82 and 83 times that of the Sun. The dense streams of matter steadily ejected by these two massive stars, called stellar winds, collide with each other and produce large amounts of X-ray emissions. But alas, no chocolate candies.

This collision is seen at different angles as the stars orbit around each other every 3.7 days.

Several other bright X-ray sources may also show evidence for collisions between winds in massive binary systems.

The Chandra image of Westerlund 2 shows low energy X-rays in red, intermediate energy X-rays in green and high energy X-rays in blue. This is an area that is incredibly dense with massive stars, and bright with X-rays.

Image is 8.4 arc minutes across and was taken by the Chandra Advanced CCD Imaging Spectrometer, which can study temperature variations from x-ray sources.

Download this image for your desktop here.

Original News Source: Chandra Photo Album