Archive

Archive for August 1, 2013

Under Leaden Skies – Where Heavy Metal Clouds The Stars


Artist's impression of the surface of HE2359-2844. Images created using POV-Ray by C. S. Jeffery.

Artist’s impression of the surface of HE2359-2844. Images created using POV-Ray by C. S. Jeffery.

In a paper shortly to be published in the Oxford University Press journal Monthly Notices of the Royal Astronomical Society, a team of astronomers from the Armagh Observatory in Northern Ireland report the discovery of two unusual stars with extremely high concentrations of lead in their atmospheres.

Naslim Neelamkodan, Simon Jeffery, Natalie Behara and Alan Hibbert are studying the surfaces of small hot stars, known as helium-rich subdwarfs. They are already known to be peculiar because they contain much less hydrogen and much more helium than normal.

The astronomers studied the stars using observations from the archives of the European Southern Observatory’s Very Large Telescope in Chile.The light signatures, or spectra, of both stars showed a few features which did not match any atoms expected to be present. After some detective work, the team realised that the features were due to lead.

Full Story: http://www.ras.org.uk/news-and-press/224-news-2013/2322-under-leaden-skies

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Spitzer Discovers Young Stars With A ‘Hula Hoop’


Artist's impression. Image credit: NASA/JPL-Caltech

Artist’s impression. Image credit: NASA/JPL-Caltech

Astronomers using NASA’s Spitzer Space Telescope have spotted a young stellar system that “blinks” every 93 days. Called YLW 16A, the system likely consists of three developing stars, two of which are surrounded by a disk of material left over from the star-formation process.

As the two inner stars whirl around each other, they periodically peek out from the disk that girds them like a hula hoop. The hoop itself appears to be misaligned from the central star pair, probably due to the disrupting gravitational presence of the third star orbiting at the periphery of the system. The whole system cycles through bright and faint phases, with the central stars playing a sort of cosmic peek-a-boo as the tilted disk twirls around them. It is believed that this disk should go on to spawn planets and the other celestial bodies that make up a solar system.

Spitzer observed infrared light from YLW 16A, emitted by the warmed gas and dust in the disk that still swathes the young stars. Other observations came from the ground-based 2MASS survey, as well as from the NACO instrument at the European Southern Observatory’s Very Large Telescope in Chile.

Full Story: http://www.jpl.nasa.gov/news/news.php?release=2013-236

Monster Galaxies Lose Their Appetite With Age


Galaxy clusters. Image credit: NASA/JPL-Caltech/SDSS/NOAO

Galaxy clusters. Image credit: NASA/JPL-Caltech/SDSS/NOAO

Our universe is filled with gobs of galaxies, bound together by gravity into larger families called clusters. Lying at the heart of most clusters is a monster galaxy thought to grow in size by merging with neighboring galaxies, a process astronomers call galactic cannibalism.

New research from NASA’s Spitzer Space Telescope and Wide-field Infrared Survey Explorer (WISE) is showing that, contrary to previous theories, these gargantuan galaxies appear to slow their growth over time, feeding less and less off neighboring galaxies.

“We’ve found that these massive galaxies may have started a diet in the last 5 billion years, and therefore have not gained much weight lately,” said Yen-Ting Lin of the Academia Sinica in Taipei, Taiwan, lead author of a study published in the Astrophysical Journal.

Full Story: http://www.jpl.nasa.gov/news/news.php?release=2013-239

When Galaxies Switch Off


Some galaxies hit a point in their lives when their star formation is snuffed out, and they become “quenched”. Quenched galaxies in the distant past appear to be much smaller than the quenched galaxies in the Universe today. This has always puzzled astronomers — how can these galaxies grow if they are no longer forming stars? A team of astronomers has now used a huge set of Hubble observations to give a surprisingly simple answer to this long-standing cosmic riddle.

As these galaxies are no longer forming new stars, they were thought to grow by colliding and merging with other smaller quenched galaxies some five to ten times less massive. However, these mergers would require many such small galaxies floating around for the quenched population to snack on — which we do not see.

Until recently it had not been possible to explore a sufficient number of quenched galaxies, but now a team of astronomers has used observations from the Hubble COSMOS survey to identify and count these switched-off galaxies throughout the last eight billion years of cosmic history.

Full Story: http://www.spacetelescope.org/news/heic1313/

A New View On The Origin Of Dark Matter And Dark Energy – Image Of M31 Heralds The Dawn Of HSC –


 31 captured by Hyper Suprime-Cam (HSC) Credit: HSC Project/NAOJ

31 captured by Hyper Suprime-Cam (HSC) Credit: HSC Project/NAOJ

A stunning image of M 31 captured by Subaru Telescope’s Hyper-Suprime Cam (HSC) displays the fruits of international collaboration and technological sophistication aligned with cutting-edge science. In addition to providing information about a nearby galaxy that resembles our own, this image demonstrates HSC’s capability to fulfill Subaru Telescope’s intention of producing a large-scale survey of the Universe. The combination of a large mirror, a wide field of view, and sharp imaging represents a giant step into a new era of observational astronomy and will contribute to answering questions about the nature of dark energy and matter. It marks another successful stage in HSC’s commissioning process, which involves checking all of HSC’s capabilities before it is ready for open use.

HSC’s first beautiful image of M 31 gives an answer to the question: Does HSC really deliver what it promises in terms of image quality? It displays a resounding “yes” by demonstrating the sharp, detailed resolution of which the camera is capable across the wide field of view that it embraces. The image indicates why this powerful instrument is unique within the domain of current observational technology, enabling high-resolution images from observations with a large primary mirror (8.2 m) and large field of view (1.5 degrees).

Full Story: http://www.ipmu.jp/ja/node/1663