The team, led by the Max Planck Institute for Astrophysics (MPA), used the database they created and were able to apply information theory techniques to produce the map, explains NRL's Dr. Tracy Clarke, a member of the research team.

"The key to applying these new techniques is that this project brings together over 30 researchers with 26 different projects and more than 41,000 measurements across the sky. The resulting database is equivalent to peppering the entire sky with sources separated by an angular distance of two full moons." This incredible volume of data results in a new, unique all-sky map that gives scientists the ability to measure the magnetic field structure of the Milky Way in unparalleled detail.

The map shows scientists a quantity known as Faraday depth, a concept that depends on magnetic fields along a specific line of sight. The research team created the map by combining the more than 41,000 individual measurements using a unique image reconstruction technique. The researchers at MPA are specialists in the new discipline of information field theory.

Dr. Tracy Clarke, working in NRL's Remote Sensing Division, is part of the team of international radio astronomers who provided the radio observations for the database. The new, high-precision map not only shows the Galactic magnetic field's structure on large scales, it also reveals small-scale features that help scientists better understand turbulence in the Galactic gas.

The Milky Way, along with all other galaxies, possesses magnetic fields. Until now, scientists have been puzzled over the origin of these galactic magnetic fields. The assumption was that the magnetic fields were created by processes where mechanical energy is converted into magnetic energy.

These same kinds of processes occur in the interior of the Earth and the Sun. The map that the team has created will give scientists valuable knowledge about the structure of Galactic magnetic fields throughout the Milky Way.

For 150 years, scientists have measured cosmic magnetic field by observing the Faraday effect. They know that when polarized light passes though a magnetized medium, the plane of polarization turns. This concept is called Faraday rotation. The strength and direction of the magnetic field governs the amount of rotation that occurs. So scientists observe the rotation to investigate the magnetic fields' properties.

Radio astronomers study the polarized light from distant radio source, passing through the Milky Way on the way to Earth, in order to measure our Galaxy's magnetic field. By measuring the polarization of the light sources at different frequencies, researchers can determine the amount of Faraday rotation.

With these individual measurements, researchers gain data about only a single path through the Galaxy. To gain a fuller picture of the Milky Way's magnetic fields from the Faraday rotation measurements, researchers have to observe many sources across the sky.

To achieve this map, radio astronomers from around the world have pooled data from 26 different projects, collecting a total of 41,330 individual measurements. The map contains approximately one radio source per square degree of sky.

Despite this large catalog of date, there are still some large areas, especially in the southern sky, where only a few measurements have been recorded. So to gain a realistic map of the entire sky, researchers have to interpolate between the existing data points that they do have recorded.

There are some difficulties in obtaining the map data this way. First, the accuracy of the various measurements varies greatly although the more exact measurements should have the greatest influence. However scientists are not certain exactly how reliable any single measurement is in providing dependable information about the environment around it. Therefore more accurate measurements are not always given the highest priority.

There is also the problem of the uncertainty of the measurements simply because the process for obtaining the measurements is highly complex. A seemingly small error can impact the data in a significant way, leading to a distorted map.

To address these problems, the MPA scientists have developed an algorithm used to reconstruct the images. This algorithm, called the "extended critical filter," uses tools provided by the new discipline known as information field theory.

Information field theory, which uses logical and statistical methods applied to fields, is an effective tool for dealing with erroneous information. Besides astronomy these tools can be used in fields such as medicine or geography for a range of image and signal-processing applications.

While the new map is particularly important for studying our own Galaxy, researchers will also be able to use it for future studies for extragalactic magnetic fields. This is possible because the scientists will use the new map to help them account for the Galactic contribution to observed Faraday rotation.

In the near future astronomers are looking toward a new generation of radio telescopes, such as LOFAR, eVLA, ASKAP, MeerKAT and the SKA that will provide an abundance of measurements of the Faraday effect. With this new data, researchers will be able to provide updates to the image of the Faraday sky, and perhaps someday understand the origin of the galactic magnetic fields.

]]> Thu, 09 FEB 2012 08:59:24 AEST San Antonio TX (SPX) Feb 06, 2012 - Using data from NASA's Interstellar Boundary Explorer (IBEX) spacecraft, an international team of researchers has measured neutral "alien" particles entering our solar system from interstellar space. A suite of studies published in the Astrophysical Journal provide a first look at the constituents of the interstellar medium, the matter between star systems, and how they interact with our heliosphere.

The heliosphere, the "bubble" in which our Sun and planets reside, is formed by the interaction between the solar wind, flowing outward from the Sun, and the interstellar medium, which presses up against it. Electrically charged, or ionized, particles cannot penetrate the boundary between these two bodies. However, neutral particles, which make up about half the material outside the heliosphere, flow freely in through the boundary.

The only other spacecraft to directly detect these inflowing neutral particles was Ulysses, which more than a decade ago measured interstellar neutral helium.

Although IBEX is designed primarily to map the interactions between the solar wind and ionized interstellar material, its low-energy energetic neutral atom camera has now also measured interstellar neutral particles not detected by Ulysses. From its location within Earth's orbit, IBEX has sampled interstellar hydrogen, oxygen, and neon in addition to neutral helium.

Neon and oxygen reside throughout the galaxy, but researchers are unsure of their distribution. Using IBEX data, the first direct measurements of these elements in the local interstellar medium, researchers can determine how much oxygen is in the local part of the galaxy, which materials are present in what amounts and more.

"Answering these questions is important for understanding the variability of the galactic soup - the material from which stars, planets and life all form," says Dr. David J. McComas, IBEX principal investigator and an assistant vice president at Southwest Research Institute.

For example, the presence of less oxygen in the local interstellar medium compared to the Sun and galactic average could indicate the Sun formed in a region with less oxygen than exists in its current location. Another possibility is that the oxygen could be preferentially tied up or "hidden" in other galactic materials, such as dust grains and ices.

IBEX data reveal that interstellar neutrals enter the heliosphere at a speed of about 52,000 mph, roughly, 7,000 mph slower than inferred from Ulysses observations, and that they enter from a somewhat different direction. Magnetic forces play a major role in the interactions of the charged particles at the heliosphere's boundaries. As the overall particle speeds drop, however, the magnetic forces play an even more dominant role.

"With this lower speed, the external magnetic forces cause the heliosphere to become more squished and misshapen," says McComas. "Rather than being shaped like a bullet moving through the air, the heliosphere becomes flattened, more like a beach ball being squeezed when someone sits on it."

Based on the older Ulysses data, researchers had theorized that the heliosphere was leaving the local galactic cloud and transitioning into a new region of space. However, while the boundary is very close, IBEX results show the heliosphere remains fully in the local cloud, at least for the moment.

"Sometime in the next hundred to few thousand years, the blink of an eye on the timescales of the galaxy, our heliosphere should leave the local interstellar cloud and encounter a much different galactic environment," McComas says.

Researchers will be able to add measurements about the charged particles outside the heliosphere to the neutral particle measurements provided by IBEX as the two Voyager spacecraft leave our solar system and cross the heliopause, possibly within the next few years.

"That will give us an even more complete picture of what's happening in the regions surrounding our home in the solar system," says McComas.

The six papers detailing the new IBEX results and an editorial written by McComas were published in a Special Supplements issue of the Astrophysical Journal called "Interstellar Boundary Explorer (IBEX): Direct Sampling of the Interstellar Medium."

The authors represent an international team of researchers from Southwest Research Institute, the University of Bern, Switzerland, the Polish Academy of Sciences Space Research Centre, the University of New Hampshire, the University of Chicago and the Massachusetts Institute of Technology.

IBEX is the latest in NASA's series of low-cost, rapidly developed Small Explorer space missions. Southwest Research Institute in San Antonio leads and developed the mission with a team of national and international partners. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the Explorers Program for NASA's Science Mission Directorate in Washington.

]]> Thu, 09 FEB 2012 08:59:24 AEST Washington DC (SPX) Feb 06, 2012 - NASA's Interstellar Boundary Explorer (IBEX) has captured the best and most complete glimpse yet of what lies beyond the solar system. The new measurements give clues about how and where our solar system formed, the forces that physically shape our solar system, and the history of other stars in the Milky Way.

The Earth-orbiting spacecraft observed four separate types of atoms including hydrogen, oxygen, neon and helium. These interstellar atoms are the byproducts of older stars, which spread across the galaxy and fill the vast space between stars.

IBEX determined the distribution of these elements outside the solar system, which are flowing charged and neutral particles that blow through the galaxy, or the so-called interstellar wind.

"IBEX is a small Explorer mission and was built with a modest investment," said Barbara Giles, director of the Heliophysics Division at NASA Headquarters in Washington. "The science achievements though have been truly remarkable and are a testament to what can be accomplished when we give our nation's scientists the freedom to innovate."

In a series of science papers appearing in the Astrophysics Journal , scientists report finding 74 oxygen atoms for every 20 neon atoms in the interstellar wind. In our own solar system, there are 111 oxygen atoms for every 20 neon atoms. This translates to more oxygen in any part of the solar system than in nearby interstellar space.

"Our solar system is different than the space right outside it, suggesting two possibilities," says David McComas, IBEX principal investigator, at the Southwest Research Institute in San Antonio.

"Either the solar system evolved in a separate, more oxygen-rich part of the galaxy than where we currently reside, or a great deal of critical, life-giving oxygen lies trapped in interstellar dust grains or ices, unable to move freely throughout space."

The new results hold clues about the history of material in the universe. While the big bang initially created hydrogen and helium, only the supernovae explosions at the end of a star's life can spread the heavier elements of oxygen and neon through the galaxy. Knowing the amounts of elements in space may help scientists map how our galaxy evolved and changed over time.

Scientists want to understand the composition of the boundary region that separates the nearest reaches of our galaxy, called the local interstellar medium, from our heliosphere. The heliosphere acts as a protective bubble that shields our solar system from most of the dangerous galactic cosmic radiation that otherwise would enter the solar system from interstellar space.

IBEX measured the interstellar wind traveling at a slower speed than previously measured by the Ulysses spacecraft, and from a different direction. The improved measurements from IBEX show a 20 percent difference in how much pressure the interstellar wind exerts on our heliosphere.

"Measuring the pressure on our heliosphere from the material in the galaxy and from the magnetic fields out there will help determine the size and shape of our solar system as it travels through the galaxy," says Eric Christian, IBEX mission scientist, at NASA's Goddard Space Flight Center in Greenbelt, Md.

The IBEX spacecraft was launched in October 2008. Its science objective is to discover the nature of the interactions between the solar wind and the interstellar medium at the edge of our solar system.

]]> Thu, 09 FEB 2012 08:59:24 AEST Munich, Germany (SPX) Feb 06, 2012 - Pulsars are among the most exotic celestial bodies known. They have diameters of about 20 kilometres, but at the same time roughly the mass of our sun. A sugar-cube sized piece of its ultra-compact matter on the Earth would weigh hundreds of millions of tons. A sub-class of them, known as millisecond pulsars, spin up to several hundred times per second around their own axes.

Previous studies reached the paradoxical conclusion that some millisecond pulsars are older than the universe itself. The astrophysicist Thomas Tauris from the Max Planck Institute for Radio Astronomy and the Argelander Institute for Astronomy in Bonn could resolve this paradox by computer simulations.

Through numerical calculations on the base of stellar evolution and accretion torques, he demonstrated that millisecond pulsars loose about half of their rotational energy during the final stages of the mass-transfer process before the pulsar turns on its radio beam.

This result is in agreement with current observations and the findings also explain why radio millisecond pulsars appear to be much older than the white dwarf remnants of their companion stars - and perhaps why no sub-millisecond radio pulsars exist at all. The results are reported in the February 03 issue of the journal Science.

Millisecond pulsars are strongly magnetized, old neutron stars in binary systems which have been spun up to high rotational frequencies by accumulating mass and angular momentum from a companion star. Today we know of about 200 such pulsars with spin periods between 1.4-10 milliseconds. These are located in both the Galactic Disk and in Globular Clusters.

Since the first millisecond pulsar was detected in 1982, it has remained a challenge for theorists to explain their spin periods, magnetic fields and ages. For example, there is the "turn-off" problem, i.e. what happens to the spin of the pulsar when the donor star terminates its mass-transfer process?

"We have now, for the first time, combined detailed numerical stellar evolution models with calculations of the braking torque acting on the spinning pulsar", says Thomas Tauris, the author of the present study. "The result is that the millisecond pulsars loose about half of their rotational energy in the so-called Roche-lobe decoupling phase."

This phase describes the termination of the mass transfer in the binary system. Hence, radio-emitting millisecond pulsars should spin slightly slower than their progenitors, X-ray emitting millisecond pulsars which are still accreting material from their donor star.

This is exactly what the observational data seem to suggest. Furthermore, these new findings help explain why some millisecond pulsars appear to have characteristic ages exceeding the age of the Universe and perhaps why no sub-millisecond radio pulsars exist.

The key feature of the new results is that it has now been demonstrated how the spinning pulsar is able to break out of its so-called equilibrium spin. At this epoch the mass-transfer rate decreases which causes the magnetospheric radius of the pulsar to expand and thereby expell the collapsing matter like a propeller. This causes the pulsar to loose additional rotational energy and thus slow down its spin rate.

"Actually, without a solution to the "turn-off" problem we would expect pulsars to even slow down to spin periods of 50-100 milliseconds during the Roche-lobe decoupling phase", concludes Thomas Tauris. "That would be in clear contradiction with observational evidence for the existence of millisecond pulsars."

The stellar evolution models used for this work were made using state-of-the-art code developed by Norbert Langer. A significant part of the observational data was supplied by the pulsar group. Michael Kramer and his colleagues use the 100 metre Effelsberg Radio Telescope to participate in several ongoing searches and discoveries of millisecond pulsars.

This work has profited from a recent effort to bridge the Stellar Physics group at the Argelander Institute for Astronomy at University of Bonn (led by Norbert Langer) with the Fundamental Physics in Radio Astronomy group at the Max Planck Institute for Radio Astronomy (led by Michael Kramer).

]]> Thu, 09 FEB 2012 08:59:24 AEST Paris, France (SPX) Feb 06, 2012 - NGC 3324 is located in the southern constellation of Carina (The Keel, part of Jason's ship the Argo) roughly 7500 light-years from Earth. It is on the northern outskirts of the chaotic environment of the Carina Nebula, which has been sculpted by many other pockets of star formation (eso0905).

A rich deposit of gas and dust in the NGC 3324 region fuelled a burst of starbirth there several millions of years ago and led to the creation of several hefty and very hot stars that are prominent in the new picture.

Stellar winds and intense radiation from these young stars have blown open a hollow in the surrounding gas and dust. This is most in evidence as the wall of material seen to the centre right of this image.

The ultraviolet radiation from the hot young stars knocks electrons out of hydrogen atoms, which are then recaptured, leading to a characteristic crimson-coloured glow as the electrons cascade through the energy levels, showing the extent of the local diffuse gas. Other colours come from other elements, with the characteristic glow from doubly ionised oxygen making the central parts appear greenish-yellow.

As with clouds in the Earth's sky, observers of nebulae can find likenesses within these cosmic clouds. One nickname for the NGC 3324 region is the Gabriela Mistral Nebula, after the Nobel Prize-winning Chilean poet [1]. The edge of the wall of gas and dust at the right bears a strong resemblance to a human face in profile, with the "bump" in the centre corresponding to a nose.

The power of the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory also reveals many dark features in NGC 3324. Dust grains in these regions block out the light from the background glowing gas, creating shadowy, filigree features that add another layer of evocative structure to the rich vista.

The sharp sight of the Hubble Space Telescope has also been trained on NGC 3324 in the past. Hubble can pick out finer details than the panoramic view of the Wide Field Imager, but only over a much smaller field of view. The two instruments when used in tandem can provide both "zoomed-in" and "zoomed-out" perspectives.

Notes
[1] Further explanation and comparison images can be found on the site of the amateur astronomer Daniel Verschatse

]]> Thu, 09 FEB 2012 08:59:24 AEST Tempe AZ (SPX) Feb 06, 2012 - For his discoveries about the lives and deaths of stars, the exotic physics of black holes and the origin of chemical elements, UA Regents' Professor David Arnett has been honored with the Henry Norris Russell Lectureship.

What happens when a star dies? How does a black hole form? What makes the chemical elements that form the building blocks of stars, planets and living beings?

Those are the kinds of questions that have fascinated David Arnett, a Regents' Professor at the University of Arizona's Steward Observatory, from an early age.

A theoretical physicist and a pioneer in the field of complex simulations, Arnett worked with the first supercomputers in the 1960s to unravel some of the greatest mysteries of the universe: how stars forge chemical elements in their cores and seed the universe when they blow up as supernovae, and how some of them turn into bizarre cosmic phenomena such as neutron stars or black holes.

In honor of his lifetime contributions, Arnett has received the Henry Norris Russell Lectureship from the American Astronomical Society, or AAS, an honor that he shares with other scientists of the caliber to have had telescopes or buildings named after them. Only two other UA researchers - Lunar and Planetary Lab founder Gerard Kuiper and former Steward Observatory Director Bart Bok - have received this recognition.

In one of his most significant achievements, Arnett predicted stellar explosions now identified with type IA supernovae. While some stars simply fizzle out when they run out of nuclear fuel, slowly cooling off by radiating what is left of their energy into the cold universe over billions of years, others end their existence in the most spectacular way imaginable: torn apart in the most violent explosions known in the universe: supernovae.

"Type IA supernovae are basically cosmic firecrackers," Arnett said. "They are caused by stars more massive than our sun but not massive enough to collapse to form a neutron star or a black hole. Other types of supernovae involve such a collapse."

Arnett's simulations revealed that type IA supernovae go through a highly consistent sequence of events, a feat that has made them invaluable to astronomers trying to get a grip on the distances of objects such as stars and galaxies and the speeds at which they move away from each other in the expanding universe.

Because their brightness curve follows a predictable pattern, scientists came to rely on type IA supernovae as cosmic yardsticks, marking distances in the universe like candles lighting the way into an unknown stretch of darkness.

Much effort at present involves so-called core-collapse supernovae, Arnett said.

"The ultimate goal of these simulations is to better understand how stars collapse. We do not know what the range of variation is, because we don't know what happens to their spin as they contract."

He pointed out that the results apply not only to dying stars but to pulsating stars, too.

"The implications are very broad," he said, "and I love that because I'm basically a physicist at heart. I love to use physics to understand what stars do. And the amazing thing is, it's working."

Less than two years ago, Arnett helped discover yet another unknown type of supernova by performing calculations that explained the puzzling distributions of chemical elements in the supernova remnant, the "smoking gun" of the stellar explosion.

Arnett, who grew up in rural Kentucky, found himself fascinated with stars at an early age and spent much of his time growing up with his eye pressed to the viewfinder of his telescope in the backyard.

"I have always been fascinated with the stars and the universe, although I don't really remember when it started," he said. "I remember my cousin and I were writing science fiction stories when we were in the fourth grade."

A book by renowned English astronomer Fred Hoyle - who is credited with coining the term "Big Bang" - advertised in an issue of Scientific American when Arnett was in high school would provide the initial spark for a life-long career studying the lives and deaths of stars.

"It was a popular book but fairly well packed with physical insight," he said. "And Fred's writing style was very clear. My family for many years had been teachers, and I wanted to be a scientist."

After receiving his bachelor's of science in physics at the University of Kentucky in 1961, Arnett gained entrance - as a "gamble" as he put it - to Yale University for graduate school.

"I say 'gamble' because I was from Kentucky, and you don't know many hillbilly astrophysicists," he said with a chuckle.

Arnett, who knows how to play banjo and guitar - bluegrass and classical style - has hardly ever used a telescope to study the physics of cosmic phenomena because he "preferred staying up late to party instead of staying up late to observe," as he put it, adding that the Kellogg Lab parties at Caltech were memorable.

Instead, he has relied on mathematical equations and supercomputers to simulate the extremely complex events going on inside stars during their lifetime and when they end their existence.

It turns out that all the heavier elements in the universe, such as iron, carbon and oxygen, and other ingredients that make up planets, rocks and living creatures, owe their existence to dying stars.

Forged under the immense pressures of a collapsing stellar core, it takes the cataclysmic explosion of a supernova to seed the universe with those elements and create new worlds and ultimately, life forms.

Studying the fluid dynamics inside stars, Arnett discovered that those flow patterns are "primarily determined by the same mechanisms that cause the flows in the atmosphere or the oceans."

"It's all physics," he said. "So there is an enormous overlap. And if you write down the equations, you can get results that apply to a lot of particular different venues, not just stars."

"We are talking about turbulence, we are talking about the convection zones of the sun, the spin of a pre-supernova, on and on, even down to the water circling the drain in your tub. It's wonderful."

Before he joined the UA almost 25 years ago, Arnett was a faculty member at the University of Chicago.

"I loved the university, but living in the inner city was a challenge for me and my family," he said. "We were in love with the desert southwest. There are not many places you can go that are active in astronomy. And this was one. "

Of his time at the UA, he said: "Probably the best thing has been my recent research, which I have done with my last three graduate students in this department."

"It's involved with three dimensional simulation of turbulent flow inside stars and that is the problem we have to solve if we want to understand how the angular momentum is distributed, the spin. Now, with astroseismology and space telescopes COROT and Kepler, we actually can look inside stars. Spin increases as stars contract, and is vital to understanding how neutron stars and black holes form.

About his field of research, Arnett said, "It has been a wonderful field to work in because it has been blossoming for the last 50 years, and it's very international. In a time when our country in so many respects is getting so insular, it's wonderful to be working with colleagues scattered across the globe. I consider that an enormous benefit for a boy that grew up in farming country."

]]> Thu, 09 FEB 2012 08:59:24 AEST Boston MA (SPX) Feb 06, 2012 - Vital clues about the devastating ends to the lives of massive stars can be found by studying the aftermath of their explosions. In its more than twelve years of science operations, NASA's Chandra X-ray Observatory has studied many of these supernova remnants sprinkled across the Galaxy.

The latest example of this important investigation is Chandra's new image of the supernova remnant known as G350.1+0.3. This stellar debris field is located some 14,700 light years from the Earth toward the center of the Milky Way.

Evidence from Chandra and from ESA's XMM-Newton telescope suggest that a compact object within G350.1+0.3 may be the dense core of the star that exploded. The position of this likely neutron star, seen by the arrow pointing to "neutron star" in the inset image, is well away from the center of the X-ray emission.

If the supernova explosion occurred near the center of the X-ray emission then the neutron star must have received a powerful kick in the supernova explosion.

Data from Chandra and other telescopes suggest this supernova remnant, as it appears in the image, is between 600 and 1,200 years old. If the estimated location of the explosion is correct, this means that the neutron star has been moving at a speed of at least 3 million miles per hour since the explosion This is comparable to the exceptionally high speed derived for the neutron star in Puppis A, another neutron star moving at a blistering pace within a supernova remnant.

The G350+1+0.3 data provide new evidence that extremely powerful "kicks" may be imparted to neutron stars left behind once the supernova has exploded.

Another intriguing aspect of G350.1+0.3 is its unusual shape. While many supernova remnants are nearly circular, G350.1+0.3 is strikingly asymmetrical as seen in the Chandra data in this image (gold). Infrared data from NASA's Spitzer Space Telescope (light blue) also trace the morphology found by Chandra. Astronomers think that this bizarre shape is due to stellar debris field expanding into a nearby cloud of cold molecular gas.

The age of 600-1200 years puts the explosion that created G350.1+0.3 in the same time frame as other famous supernovas that formed the Crab and SN 1006 supernova remnants. However, it is unlikely that anyone on Earth would have seen the explosion because of the obscuring gas and dust that lies along our line of sight to the remnant.

These results appeared in the April 10, 2011 issue of The Astrophysical Journal. The scientists on this paper were Igor Lovchinsky and Patrick Slane (Harvard-Smithsonian Center for Astrophysics), Bryan Gaensler (University of Sydney, Australia), Jack Hughes (Rutgers University), Jasmina Lazendic (Monash University Clayton, Australia), Joseph Gelfand (New York University, Abu Dhabi), and Crystal Brogan (National Radio Astronomy Observatory).

]]> Thu, 09 FEB 2012 08:59:24 AEST Greenbelt MD (SPX) Feb 02, 2012 - A great magnetic bubble surrounds the solar system as it cruises through the galaxy. The sun pumps the inside of the bubble full of solar particles that stream out to the edge until they collide with the material that fills the rest of the galaxy, at a complex boundary called the heliosheath.

On the other side of the boundary, electrically charged particles from the galactic wind blow by, but rebound off the heliosheath, never to enter the solar system. Neutral particles, on the other hand, are a different story. They saunter across the boundary as if it weren't there, continuing on another 7.5 billion miles for 30 years until they get caught by the sun's gravity, and sling shot around the star.

There, NASA's Interstellar Boundary Explorer lies in wait for them. Known as IBEX for short, this spacecraft methodically measures these samples of the mysterious neighborhood beyond our home.

IBEX scans the entire sky once a year, and every February, its instruments point in the correct direction to intercept incoming neutral atoms. IBEX counted those atoms in 2009 and 2010 and has now captured the best and most complete glimpse of the material that lies so far outside our own system.

The results? It's an alien environment out there: the material in that galactic wind doesn't look like the same stuff our solar system is made of.

"We've directly measured four separate types of atoms from interstellar space and the composition just doesn't match up with what we see in the solar system," says Eric Christian, mission scientist for IBEX at NASA's Goddard Space Flight Center in Greenbelt, Md. "IBEX's observations shed a whole new light on the mysterious zone where the solar system ends and interstellar space begins."

More than just helping to determine the distribution of elements in the galactic wind, these new measurements give clues about how and where our solar system formed, the forces that physically shape our solar system, and even the history of other stars in the Milky Way.

In a series of science papers appearing in the Astrophysics Journal on January 31, 2012, scientists report that for every 20 neon atoms in the galactic wind, there are 74 oxygen atoms. In our own solar system, however, for every 20 neon atoms there are 111 oxygen atoms. That translates to more oxygen in any given slice of the solar system than in the local interstellar space.

"Our solar system is different than the space right outside it and that suggests two possibilities," says David McComas the principal investigator for IBEX at the Southwest Research Institute in San Antonio, Texas.

"Either the solar system evolved in a separate, more oxygen-rich part of the galaxy than where we currently reside or a great deal of critical, life-giving oxygen lies trapped in interstellar dust grains or ices, unable to move freely throughout space." Either way, this affects scientific models of how our solar system - and life - formed.

Studying the galactic wind also provides scientists with information about how our solar system interacts with the rest of space, which is congruent with an important IBEX goal.

Classified as a NASA Explorer Mission - a class of smaller, less expensive spacecraft with highly focused research objectives - IBEX's main job is to study the heliosheath, that outer boundary of the solar system's magnetic bubble - or heliosphere - where particles from the solar wind meet the galactic wind.

Previous spacecraft have already provided some information about the way the galactic wind interacts with the heliosheath. Ulysses, for one, observed incoming helium as it traveled past Jupiter and measured it traveling at 59,000 miles per hour. IBEX's new information, however, shows the galactic wind traveling not only at a slower speed - around 52,000 miles per hour - but from a different direction, most likely offset by some four degrees from previous measurements.

Such a difference may not initially seem significant, but it amounts to a full 20% difference in how much pressure the galactic wind exerts on the heliosphere.

"Measuring the pressure on our heliosphere from the material in the galaxy and from the magnetic fields out there," says Christian, "will help determine the size and shape of our solar system as it travels through the galaxy."

These IBEX measurements also provide information about the cloud of material in which the solar system currently resides. This cloud is called the local interstellar cloud, to differentiate it from the myriad of particle clouds throughout the Milky Way, each traveling at different speeds. The solar system and its heliosphere moved into our local cloud at some point during the last 45,000 years.

Since the older Ulysses observations of the galactic wind speed was in between the speeds expected for the local cloud and the adjacent cloud, researchers thought perhaps the solar system didn't lie smack in the middle of this cloud, but might be at the boundary, transitioning into a new region of space.

IBEX's results, however, show that we remain fully in the local cloud, at least for the moment.

"Sometime in the next hundred to few thousand years, the blink of an eye on the timescales of the galaxy, our heliosphere should leave the local interstellar cloud and encounter a much different galactic environment," McComas says.

In addition to providing insight into the interaction between the solar system and its environment, these new results also hold clues about the history of material in the universe.

While the big bang initially created hydrogen and helium, only the supernovae explosions at the end of a giant star's life can spread the heavier elements of oxygen and neon through the galaxy. Knowing the amounts of such elements in space can help map how the galaxy has evolved and changed over time.

"This set of papers provide many of the first direct measurements of the interstellar medium around us," says McComas. "We've been trying to understand our galaxy for a long time, and with all of these observations together, we are taking a major step forward in knowing what the local part of the galaxy is like."

Voyager 1 could cross out of our solar system within the next few years. By combining the data from several sets of NASA instruments - Ulysses, Voyager, IBEX and others - we are on the precipice of stepping outside and understanding the complex environment beyond our own frontier for the first time.

The Southwest Research Institute developed and leads the IBEX mission with a team of national and international partners. The spacecraft is one of NASA's series of low-cost, rapidly developed missions in the Small Explorers Program. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the program for the agency's Science Mission Directorate.

]]> Thu, 09 FEB 2012 08:59:24 AEST Washington DC (SPX) Jan 31, 2012 - A Naval Research Laboratory scientist is part of a team that has recently discovered that vast clouds of hot gas are "sloshing" in Abell 2052, a galaxy cluster located about 480 million light years from Earth. The scientists are studying the hot (30 million degree) gas using X-ray data from NASA's Chandra X-ray Observatory and optical data from the Very Large Telescope to see the galaxies.

"The X-ray images were amazing. We were able to see gas sloshing like liquid in a glass" explains NRL's Dr. Tracy Clarke. "Of course this would be one enormous glass since we see the gas sloshing over a region of nearly a million light years across!"

The Chandra data reveal the huge spiral structure in the hot gas around the outside of the image. Zooming in on the cluster reveals "cavities" or "bubbles" surrounding the central giant elliptical galaxy. The spiral began when a small cluster of galaxies collided off-center with a larger one positioned around that central galaxy.

The gravitational attraction of the smaller cluster drew the hot gas out of the central cluster toward the smaller cluster. Once the smaller cluster passed by the central cluster core, the gas movement reversed and it was pulled back toward the center of the main cluster.

The hot cluster gas overshot the cluster center, creating the "sloshing" effect that is like the sloshing that occurs when a glass holding a liquid is quickly jerked sideways. In the cluster, gravity pulls back on the gas cloud, creating the spiral pattern.

For scientists, the observation of the "sloshing" motion in Abell 2052 is important for two reasons. First, the "sloshing" helps to move some of the cooler, dense gas in the center of the core farther away from the core.

This cooler gas is only about 10 million degrees, as compared to the average temperature of 30 million degrees. This movement reduces the amount of cooling in the cluster core and could limit the amount of new stars being formed in the central galaxy.

The "sloshing" movement in Abell 2052 also helps redistribute heavy elements like iron and oxygen, which are created out of supernova explosions. These heavy elements are an important part of the make-up of future stars and planets. The fact that Chandra's observation of Abell 2052 lasted more than a week was critical in providing scientists with the details detected in this image.

Besides the large-scale spiral feature, the Chandra observations also allowed scientists to see details in the center of the cluster related to outbursts from the supermassive black hole. The data reveal bubbles resulting from material blasted away from the black hole which are surrounded by dense, bright, cool rims.

In the same way that the "sloshing" helps to reduce the cooling of the gas at the core of the cluster, the bubble activity has the same effect, limiting the growth of the galaxy and its supermassive black hole.

This research was published in the August 20, 2011 issue of The Astrophysical Journal. The authors were Elizabeth Blanton of Boston University, Boston, MA; Scott Randall of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA; Tracy Clarke of the Naval Research Laboratory, Remote Sensing Division, in Washington DC; Craig Sarazin of the University of Virginia in Charlottesville, VA; Brian McNamara of the University of Waterloo in Waterloo, Canada; Edmund Douglass of Boston University and Michael McDonald of the University of Maryland, College Park, MD.

]]> Thu, 09 FEB 2012 08:59:24 AEST Paris, France (ESA) Jan 30, 2012 - Astronomers studying the Vela pulsar wind nebula with ESA's INTEGRAL observatory have successfully resolved its morphology in the hard X-ray band, for the first time. This pulsar-powered nebula is the most extended individual source yet observed at these energies. The study exploited a special imaging technique to reveal a new component of the source that likely consists of highly energetic electrons that have escaped from the core of the nebula in the last few thousand years.

One of the milestones in modern astrophysics was the discovery, in the late 1960s, of the Vela and Crab pulsars. These pulsating sources were the first of their kind to be detected within the remnants of supernova explosions. By providing the first evidence for a causal link between the then recently discovered class of sources and the demise of massive stars, these observations clarified the nature of pulsars: rapidly spinning and strongly magnetised neutron stars.

Like all pulsars powered by their own rotation, the Vela pulsar gradually releases its rotational kinetic energy by driving a steady wind of highly energetic electrons and positrons. Pulsar winds create clouds of charged particles, known as pulsar wind nebulae (PWN), that radiate energy across the electromagnetic spectrum and are thus observable in several bands.

During its early phases, the highly pressurised PWN expands at high speed in its denser environment, which consists of ejected material from the supernova explosion that created the pulsar and swept up material from the surrounding interstellar medium. This structure, known as a supernova remnant (SNR), in turn expands into the diffuse interstellar medium.

Interactions between the expanding components produce a number of interesting effects affecting the dynamical evolution and, subsequently, the morphology of PWN.

At a distance of about 900 light-years, the Vela PWN is one of the nearest of its kind and thus offers an opportunity for detailed investigations. It has been studied extensively at X- and gamma-ray energies, as well as in radio waves.

A recent study led by Fabio Mattana from the Laboratoire APC - AstroParticule et Cosmologie, Paris, France, has used data from ESA's INTEGRAL mission to image the Vela PWN at hard X-ray energies, between 18 and 40 keV. By resolving a PWN at these energies for the first time, the study opens up a new and revealing spectral window on these intriguing objects.

Multiwavelength observations of a PWN help to sample populations of particles with different energies that exist in the cloud. In particular, X-rays are released by electrons as they move along the pulsar's magnetic field (synchrotron emission); in contrast, gamma-ray emission arises from a different physical mechanism: the energy boost that synchrotron photons experience when they scatter off electrons (Inverse Compton emission).

This means that, somewhat counterintuitively, the most energetic particles in a PWN are revealed by observations in the hard X-ray, rather than the gamma-ray, spectral band.

"Since the most energetic particles in a PWN are the ones with the shortest lifetime, our observations of the Vela PWN in hard X-rays provide a fresh look at this source's recent history," comments Mattana.

The study used data from the IBIS imager on board INTEGRAL and applied a special data analysis technique that was developed in 2006 to further exploit the capabilities of the instrument. Originally optimised to study point sources, with this method IBIS is also suitable for the observation of extended sources and the characterisation of their morphology.

"Besides confirming the results of previous observations of the Vela PWN, which showed a cocoon-shaped cloud to the south-west of the pulsar at soft X-ray and gamma-ray wavelengths, the new INTEGRAL image reveals a previously unknown component at a rather unexpected location, north-east of the pulsar," Mattana adds.

The well-known asymmetric structure of the Vela PWN, with the 'cocoon' on one side of the pulsar, is typical of an evolved PWN. This object is in fact a prototype of PWN undergoing this phase of their evolution. As the expanding SNR sweeps up material from the surrounding interstellar medium, it produces two shock waves, moving outwards and inwards, respectively.

When the latter, known as the 'reverse' shock, eventually hits the boundary of the PWN, a few thousand years after the supernova explosion, it compresses and distorts the cloud, giving it a chaotic and filamentary structure. In the process, as a consequence of the SNR expansion into an inhomogeneous interstellar medium asymmetries in the cloud shape and displacements of the PWN with respect to the pulsar often arise.

The newly detected component, seen only in hard X-rays so far, can also be explained as an effect of the reverse shock.

"We believe that the newly-revealed region is a 'recently' born cloud, consisting of particles that have been injected by the pulsar after the supernova reverse shock has 'wiped away' the pre-existing nebula from the pulsar surroundings," explains Mattana.

"In this case, the displaced lobe would only be populated by freshly injected particles, released by the Vela pulsar in the last couple of thousand years; these shine brightly at hard X-ray energies," he adds. This scenario is also consistent with the spectral analysis of data from INTEGRAL and from the Japanese-US Suzaku mission, also performed during the same study.

Mattana and his colleagues hope that more clues about the nature of the newly-detected lobe will emerge with future observations of the source at lower X-ray energies, to be performed with ESA's XMM-Newton X-ray observatory and other facilities.

This study presents the first INTEGRAL image of extended emission around the Vela pulsar in this energy range. With an angular size of about 50 arc minutes on each side, the Vela PWN is the most extended individual source observed at hard X-ray energies thus far. It is also the first time that the application of this imaging technique has allowed a detailed investigation of the source's morphology.

"The result is a significant achievement for INTEGRAL and showcases the versatility of the instruments on board the observatory as well as the creativity of its user community," comments Chris Winkler, INTEGRAL Project Scientist at ESA. "With this technique, we have a new way to investigate the hard X-ray sky, and we look forward to its application to other sources, such as nearby supernova remnants."

The study presented here is based on observations performed with IBIS, the coded-mask imager on board INTEGRAL, with its low-energy detector ISGRI, which is sensitive to the energy range between 15 keV and 1 MeV.

As with all coded-mask imagers, IBIS does not produce images directly but via a reconstruction algorithm. The design of IBIS is optimised for the study of point sources in the hard X-ray sky and the standard reconstruction technique used to obtain images from IBIS data strongly concentrates on the portions of the sky where the radiation flux peaks.

This has the disadvantage of centralising possibly extended sources at the expense of their flux, reducing them to apparent point sources with a tenfold dimmer flux.

In order to employ IBIS to study extended sources, a novel approach has been developed to overcome this drawback. This method takes account of the telescope point spread function over the entire field of view in order to properly rescale the flux in the images.

A correct image of the source over its entire angular extent is then achieved. The method has been developed by Matthieu Renaud (currently at Laboratoire Univers et Particules de Montpellier, France) and collaborators in 2006 and is described in M. Renaud, et al. (2006).

F. Mattana, et al., "Extended Hard X-Ray Emission from the Vela Pulsar Wind Nebula", 2011, The Astrophysical Journal Letters, 743, 18 DOI: 10.1088/2041-8205/743/1/L18; M. Renaud, et al., "Imaging extended sources with coded mask telescopes: application to the INTEGRAL IBIS/ISGRI instrument", 2006, Astronomy and Astrophysics, 456, 389 DOI: 10.1051/0004-6361:20065156

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