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Archive for November, 2013

Home Computers Discover Gamma-Ray Pulsars

November 28, 2013 Leave a comment

Since its launch in 2008, the Fermi satellite has been observing the entire sky in gamma-rays. It has discovered thousands of previously unknown gamma-ray sources, among which are possibly hundreds of yet undiscovered pulsars – compact and rapidly rotating remnants of exploded stars. Identifying these new gamma-ray pulsars, however, is computationally very expensive – wide parameter ranges have to be “scanned” at very high resolution.

“Our innovative solution for the compute intensive search for gamma-ray pulsars is the combination of particularly efficient methods along with the distributed computing power of Einstein@Home,” says Holger Pletsch, Independent Research Group Leader at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI), and lead author of the study. “The volunteers from around the world enable us to deal with the huge computational challenge posed by the Fermi data analysis. In this way, they provide an invaluable service to astronomy,” says Pletsch.

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GREAT3 Challenge Seeks New Methods For Measuring Weak Gravitational Lensing

November 28, 2013 Leave a comment

Image courtesy of NASA, ESA, S. Beckwith (STScI) and the HUDF Team

Image courtesy of NASA, ESA, S. Beckwith (STScI) and the HUDF Team

Think you can figure out a way to unlock one of the biggest secrets of the universe? The recently launched third Gravitational Lensing Accuracy Testing challenge (GREAT3) is giving researchers the opportunity to do just that.

GREAT3, which is led by Carnegie Mellon University’s Rachel Mandelbaum and UCL’s (University College London’s) Barnaby Rowe, invites researchers from many fields, including astrophysics, statistics and machine learning, to test new and existing methods for measuring weak gravitational lensing. Weak gravitational lensing is one of the most direct – but also most difficult – ways scientists have to learn about the mysterious invisible dark matter and dark energy that dominates our universe.

“In previous challenges, people have come up with entirely new methods for measuring weak gravitational lensing that we are using in practice today. We’re excited to think about what people will come up with in this challenge, and to think about what new information we’ll learn about existing methods for measuring weak lensing,” said Mandelbaum, who is an assistant professor of physics and member of the McWilliams Center for Cosmology at Carnegie Mellon.

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Hyper Suprime-Cam Captures A Clear Image Of Comet ISON’s Long Tails

November 28, 2013 Leave a comment

Imaged by HSC

Imaged by HSC

During an intensive commissioning run, Hyper Suprime-Cam (HSC), mounted at prime focus on the Subaru Telescope, has successfully imaged the Comet ISON (C/2012 S1) as it journeys toward the Sun. Especially striking in the HSC image are the comet’s long tails, which span a distance more than twice the diameter of the full moon.

The observation took place in the early morning of November 5, 2013 in Hawaii during a test of non-sidereal tracking, which follows an object that moves at a different rate than the stars. Since Solar System objects such as comets and asteroids appear to move faster than more distant stars and galaxies, they require this special mode of telescope tracking, which allows observers to keep the target in view. An additional challenge for tracking Comet ISON was its low altitude of less than 30 degrees. Nevertheless, the commissioning team was able to capture a clear image of the comet and its tails, including their faint parts, which extend more than one degree away from the Sun. At the time of the observation, Comet ISON was 170 million kilometers from the Earth and 130 million kilometers from the Sun.

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Figures Of Eight And Peanut Shells: How Stars Move At The Center Of The Galaxy

November 28, 2013 Leave a comment

Two months ago astronomers created a new 3D map of stars at the centre of our Galaxy (the Milky Way), showing more clearly than ever the bulge at its core. Previous explanations suggested that the stars that form the bulge are in banana-like orbits, but a paper published this week in Monthly Notices of the Royal Astronomical Society suggests that the stars probably move in peanut-shell or figure of eight-shaped orbits instead.

The difference is important; astronomers develop theories of star motions to not only understand how the stars in our galaxy are moving today but also how our galaxy formed and evolves. The Milky Way is shaped like a spiral, with a region of stars at the centre known as the “bar,” because of its shape. In the middle of this region, there is a “bulge” that expands out vertically.

In the new paper Alice Quillen, professor of astronomy at the University of Rochester, and her collaborators created a mathematical model of what might be happening at the centre of the Milky Way. Unlike the Solar System where most of the gravitational pull comes from the Sun and is simple to model, it is much harder to describe the gravitational field near the centre of the Galaxy, where millions of stars, vast clouds of dust, and even dark matter swirl about. In this case, Quillen and her colleagues considered the forces acting on the stars in or near the bulge.

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NASA Sees ‘Watershed’ Cosmic Blast In Unique Detail

November 21, 2013 Leave a comment

On April 27, a blast of light from a dying star in a distant galaxy became the focus of astronomers around the world. The explosion, known as a gamma-ray burst and designated GRB 130427A, tops the charts as one of the brightest ever seen.

A trio of NASA satellites, working in concert with ground-based robotic telescopes, captured never-before-seen details that challenge current theoretical understandings of how gamma-ray bursts work.

“We expect to see an event like this only once or twice a century, so we’re fortunate it happened when we had the appropriate collection of sensitive space telescopes with complementary capabilities available to see it,” said Paul Hertz, director of NASA’s Astrophysics Division in Washington.

Gamma-ray bursts are the most luminous explosions in the cosmos, thought to be triggered when the core of a massive star runs out of nuclear fuel, collapses under its own weight, and forms a black hole. The black hole then drives jets of particles that drill all the way through the collapsing star and erupt into space at nearly the speed of light.

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NASA’s Chandra Helps Confirm Evidence Of Jet In Milky Way’s Black Hole

November 21, 2013 Leave a comment

Image Credit: X-ray: NASA/CXC/UCLA/Z. Li et al; Radio: NRAO/VLA

Image Credit: X-ray: NASA/CXC/UCLA/Z. Li et al; Radio: NRAO/VLA

Astronomers have long sought strong evidence that Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, is producing a jet of high-energy particles. Finally they have found it, in new results from NASA’s Chandra X-ray Observatory and the National Science Foundation’s Very Large Array (VLA) radio telescope.

Previous studies, using a variety of telescopes, suggested there was a jet, but these reports — including the orientation of the suspected jets — often contradicted each other and were not considered definitive.

“For decades astronomers have looked for a jet associated with the Milky Way’s black hole. Our new observations make the strongest case yet for such a jet,” said Zhiyuan Li of Nanjing University in China, lead author of a study appearing in an upcoming edition of The Astrophysical Journal and available online now.

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Comet ISON Brightening Fast As Its Moment Of Truth Nears

November 21, 2013 Leave a comment

Comet ISON. Credit: Damian Peach / SkyandTelescope.com

Comet ISON. Credit: Damian Peach / SkyandTelescope.com

Comet ISON, anticipated by skywatchers for more than a year, is brightening fast just days from its fateful hairpin swing on November 28th around the broiling surface of the Sun. The comet is now a greenish-white fuzzy “star” in binoculars, low in the east-southeast at the beginning of dawn. Telescopic photos are showing it with a long, ribbony tail. The comet has flared with unexpected outbursts of gas and dust three times already this month.

“We might witness a nice, long-tailed comet visible to the naked eye that will leave millions of people with fond memories for a lifetime,” says Alan MacRobert, a senior editor of Sky & Telescope magazine. “Or maybe it will be a small comet for sky hunters using binoculars and a good map of its position. Or it might yet break up and vanish.”

It all depends on what happens to the comet’s tiny nucleus, its only solid part. A comet’s nucleus is a dirty iceball that’s just a pinpoint by astronomical standards — in this case less than a mile or two across. As it flies in from the cold outer solar system and warms in the heat of the Sun, some of its ice evaporates, releasing gas and dust that expands by thousands or even millions of miles to become the comet’s glowing head (“coma”) and tail.

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Neutrinos On Ice Now The Coolest New Astronomy Tool

November 21, 2013 Leave a comment

The IceCube Lab. Credit: Sven Lidstrom. IceCube/NSF

The IceCube Lab. Credit: Sven Lidstrom. IceCube/NSF

A massive telescope buried in the Antarctic ice has detected 28 record-breaking, extremely high-energy neutrinos — elementary particles that likely originate outside our solar system. The achievement, which comes nearly 25 years after the pioneering idea of detecting neutrinos in ice, provides the first solid evidence for astrophysical neutrinos from cosmic accelerators and has been hailed as the dawn of a new age of astronomy. The team researchers that detected the neutrinos with the new IceCube Neutrino Observatory in Antarctica, which includes Penn State scientists, will publish a paper describing the detections on 22 November 2013 in the journal Science.

“While it is premature to speculate about the precise origin of these neutrinos, their energies are too high to be produced by cosmic rays interacting in the Earth’s atmosphere, strongly suggesting that they are produced by distant accelerators of subatomic particles elsewhere in our galaxy, or even farther away,” said Penn State Associate Professor of Physics Tyce DeYoung, the deputy spokesperson of the IceCube Collaboration.

The neutrinos had energies greater than 1,000,000,000,000,000 electron volts or, as the scientists say, 1 peta-electron volt (PeV). Two of these neutrinos had energies many thousands of times higher than the highest-energy neutrino that any man-made particle accelerator has ever produced.

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Hubble Reveals First Scrapbook Pictures Of Milky Way’s Formative Years

November 21, 2013 Leave a comment

Artist's Illustration of the Early Milky Way. Credit: NASA, ESA, and Z. Levay (STScI/AURA)

Artist’s Illustration of the Early Milky Way. Credit: NASA, ESA, and Z. Levay (STScI/AURA)

According to new Hubble Space Telescope observations of our Milky Way’s siblings, which existed long ago, the night sky must have looked much emptier in the distant past, when our galaxy was still under construction. The vast majority of our Milky Way’s stars had not yet been born. Yet the heavens were ablaze with a firestorm of new star formation.

By tracing the Milky Way’s siblings, astronomers find that our galaxy built up most of its stars between 11 billion and 7 billion years ago. The Hubble telescope’s superb resolving power allowed the researchers to study how the structure of Milky Way-like galaxies changed over time. The observations suggest that our galaxy’s flat disk and central bulge grew simultaneously into the majestic spiral galaxy of today.

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New Data On The Composition Of Relativistic Jets From Black Holes

November 21, 2013 Leave a comment

Artist impression. Image: Riccardo Lanfranchi

Artist impression. Image: Riccardo Lanfranchi

It is known that black holes launch relativistic jets both in stellar-mass binary systems and at the centres of galaxies, in the so-called ‘quasars’. Although jets have been studied for decades, their composition has remained uncertain. Now, a work, published on Nature and led by researchers from the University of Barcelona, the German headquarters of the European Southern Observatory (ESO) and Curtin University (Australia), presents the detection of atomic nuclei in the relativistic jets from the black hole binary system 4U 1630-47.

“In this work, we have found the composition of relativistic jets launched from around black holes; however, more studies are needed to understand if results can be extrapolated to other relativistic jet sources”, explains Simone Migliari, from the Institute of Sciences of the Cosmos of the UB (ICCUB). According to the researcher, the research proves that relativistic jets might be ‘heavy jets’ containing atomic nuclei, rather than ‘light jets’ consisting of electrons and positrons only”. “The finding —he adds— implies that ‘heavy jets’ carry away significantly more energy from the black hole than ‘lighter’ ones”.

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