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A Cloudy Mystery

January 17, 2013 Leave a comment

Mysterious galactic cloud is the black object on the left. Galactic center is the bright spot on the right. Credit: NASA/Spitzer/Benjamin et al., Churchwell et al.

Mysterious galactic cloud is the black object on the left. Galactic center is the bright spot on the right. Credit: NASA/Spitzer/Benjamin et al., Churchwell et al.

It’s the mystery of the curiously dense cloud. And astronomers at the California Institute of Technology (Caltech) are on the case.

Near the crowded galactic center, where billowing clouds of gas and dust cloak a supermassive black hole three million times as massive as the sun—a black hole whose gravity is strong enough to grip stars that are whipping around it at thousands of kilometers per second—one particular cloud has baffled astronomers. Indeed, the cloud, dubbed G0.253+0.016, defies the rules of star formation.

According to conventional wisdom, clouds of gas that are this dense should clump up to create pockets of even denser material that collapse due to their own gravity and eventually form stars. One such gaseous region famed for its prodigious star formation is the Orion Nebula. And yet, although the galactic-center cloud is 25 times denser than Orion, only a few stars are being born there—and even then, they are small. In fact, the Caltech astronomers say, its star-formation rate is 45 times lower than what astronomers might expect from such a dense cloud.

“It’s a very dense cloud and it doesn’t form any massive stars—which is very weird,” says Jens Kauffmann, a senior postdoctoral scholar at Caltech.

Full Story: http://www.caltech.edu/content/cloudy-mystery

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NASA’s GALEX Reveals The Largest-Known Spiral Galaxy

January 17, 2013 Leave a comment

Spiral Galaxy NGC 6872. Credit: NASA's Goddard Space Flight Center/ESO/JPL-Caltech/DSS

Spiral Galaxy NGC 6872. Credit: NASA’s Goddard Space Flight Center/ESO/JPL-Caltech/DSS

The spectacular barred spiral galaxy NGC 6872 has ranked among the biggest stellar systems for decades. Now a team of astronomers from the United States, Chile and Brazil has crowned it the largest-known spiral, based on archival data from NASA’s Galaxy Evolution Explorer (GALEX) mission, which has since been loaned to the California Institute of Technology, Pasadena, Calif.

Measuring tip-to-tip across its two outsized spiral arms, NGC 6872 spans more than 522,000 light-years, making it more than five times the size of our Milky Way galaxy.

“Without GALEX’s ability to detect the ultraviolet light of the youngest, hottest stars, we would never have recognized the full extent of this intriguing system,” said lead scientist Rafael Eufrasio, a research assistant at NASA’s Goddard Space Flight Center in Greenbelt, Md., and a doctoral student at Catholic University of America in Washington. He presented the findings Thursday at the American Astronomical Society meeting in Long Beach, Calif.

Full Story: http://www.nasa.gov/mission_pages/galex/galex20130110.html

Astronomers Discover The Largest Structure In The Universe

January 17, 2013 Leave a comment

An international team of astronomers, led by academics from the University of Central Lancashire (UCLan), has found the largest known structure in the universe. The large quasar group (LQG) is so large that it would take a vehicle travelling at the speed of light some 4 billion years to cross it. The team publish their results in the journal Monthly Notices of the Royal Astronomical Society.

Since 1982 it has been known that quasars tend to group together in clumps or ‘structures’ of surprisingly large sizes, forming large quasar groups or LQGs.

The team, led by Dr Roger Clowes from UCLan’s Jeremiah Horrocks Institute, has identified the LQG which is so significant in size it also challenges the Cosmological Principle: the assumption that the universe, when viewed at a sufficiently large scale, looks the same no matter where you are observing it from.

Full Story: http://www.ras.org.uk/news-and-press/224-news-2013/2212-astronomers-discover-the-largest-structure-in-the-universe

The Supernova That Cried Wolf

January 17, 2013 Leave a comment

The new SN 2009ip result suggests that stars like Eta Carinae could potentially blow up at any time. Photo: Nathan Smith/NASA

The new SN 2009ip result suggests that stars like Eta Carinae could potentially blow up at any time. Photo: Nathan Smith/NASA

Astronomers have announced that a massive star, which they have watched repeatedly mimic a supernova since 2009, has finally exploded for real. The report was presented at the American Astronomical Society meeting in Long Beach, Calif. by Jon Mauerhan of the Steward Observatory at the University of Arizona, in collaboration with Nathan Smith, also of the UA, and Alex Filippenko of the University of California, Berkeley.

The result is of special interest because it provides new critical information on the final death throes of massive stars in the years leading up to their explosion. The work has been accepted for publication in the Monthly Notices of the Royal Astronomical Society.

The object is SN 2009ip, a luminous extragalactic transient first detected in 2009 in the spiral galaxy NGC 7259, which lies 67 million light-years away in the constellation Piscis Austrinus. A “transient” is an astronomical object that can be observed for a short time. Soon after discovery in 2009, the outburst of SN 2009ip actually was recognized to be a non-terminal event, one in which the star in question survived.

Full Story: http://www.uanews.org/story/supernova-cried-wolf

A Jumble of Exotic Stars

January 17, 2013 Leave a comment

Credit: ESO’s VISTA Telescope

Credit: ESO’s VISTA Telescope

This new infrared image from ESO’s VISTA telescope shows the globular cluster 47 Tucanae in striking detail. This cluster contains millions of stars, and there are many nestled at its core that are exotic and display unusual properties. Studying objects within clusters like 47 Tucanae may help us to understand how these oddballs form and interact. This image is very sharp and deep due to the size, sensitivity, and location of VISTA, which is sited at ESO’s Paranal Observatory in Chile.

Globular clusters are vast, spherical clouds of old stars bound together by gravity. They are found circling the cores of galaxies, as satellites orbit the Earth. These star clumps contain very little dust and gas — it is thought that most of it has been either blown from the cluster by winds and explosions from the stars within, or stripped away by interstellar gas interacting with the cluster. Any remaining material coalesced to form stars billions of years ago.

Full Story and Links: http://www.eso.org/public/news/eso1302/

Astronomers Find Massive Supply Of Fresh Gas Around Modern Galaxies

January 17, 2013 Leave a comment

Galaxies have a voracious appetite for fuel — in this case fresh gas, but astronomers have had difficulty finding the pristine gas that should be falling onto galaxies. Now scientists have provided direct empirical evidence for these gas flows using new observations from the Hubble Space Telescope. Their observations using Hubble’s two ultraviolet spectrographs, the Cosmic Origins Spectrograph and the Space Telescope Imaging Spectrograph, show large quantities of cool gas with very low quantities of heavy elements in the gaseous cocoons surrounding modern galaxies. The lack of heavy elements indicates this gas in the “circumgalactic medium” of the galaxies has not been strongly processed through stars.

The team led by Nicolas Lehner, a research associate professor at the University of Notre Dame, identified gaseous streams near galaxies through the absorption they imprint on the spectra of distant, bright background quasars. The atoms in the gas remove small amounts of the light, and as the light from the quasars passes through the gas around galaxies, the chemical elements leave characteristic spectral “fingerprints” that allow astronomers to study the physical and chemical properties of the gas. Lehner and collaborators searched for the signature of gas within about 100,000 to 300,000 light-years of galaxies, identifying this gas due to its strong hydrogen absorption, a known signature of circumgalactic gas. They subsequently determined the amount of “metals” — all elements heavier than hydrogen and helium — in this gas to test whether the circumgalactic matter was being newly accreted from intergalactic space and lacking metals or being ejected from the galaxies themselves with strong metals.

Dropbox Download for Text and Data: https://www.dropbox.com/sh/a0wdv77g4mrt9b4/gvRaxI86t2

Jupiter Dances With The Moon

January 17, 2013 Leave a comment

Stargazers in the Americas have an extraordinary opportunity on the night of Monday, January 21, 2013. Jupiter, the second-brightest planet, will appear less than a finger-width from the Moon throughout North America. And in much of South America, the Moon will actually pass right in front of Jupiter, hiding it from view.

The pair is already very close together at sunset. The time of their closest approach on the evening of January 21st depends on your location; it’s around 7 p.m. in the Pacific time zone, 8:30 p.m. Mountain, 10 p.m. Central, and 11:30 p.m. Eastern time. To find out when the Moon occults (hides) Jupiter for selected locations in South America, see the International Occultation Timing Association website.

Full Story: http://www.skyandtelescope.com/about/pressreleases/Jupiter-Moon-Pairing-187136621.html