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NASA’s Chandra Finds Largest Galaxy Cluster in Early Universe

January 11, 2012 Leave a comment

X-ray: NASA/CXC/Rutgers/J. Hughes et al; Optical: ESO/VLT & SOAR/Rutgers/F. Menanteau; IR: NASA/JPL/Rutgers/F. Menanteau

An exceptional galaxy cluster, the largest seen in the distant universe, has been found using NASA’s Chandra X-ray Observatory and the National Science Foundation-funded Atacama Cosmology Telescope (ACT) in Chile.

Officially known as ACT-CL J0102-4915, the galaxy cluster has been nicknamed “El Gordo” (“the big one” or “the fat one” in Spanish) by the researchers who discovered it. The name, in a nod to the Chilean connection, describes just one of the remarkable qualities of the cluster, which is located more than seven billion light years from Earth. This large distance means that it is being observed at a young age.

“This cluster is the most massive, the hottest, and gives off the most X-rays of any known cluster at this distance or beyond,” said Felipe Menanteau of Rutgers University in New Brunswick, N.J., who led the study.

Full Story: http://www.nasa.gov/mission_pages/chandra/news/H-12-008.html

Hubble Pinpoints Farthest Protocluster of Galaxies Ever Seen

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Using NASA’s Hubble Space Telescope, astronomers have uncovered a cluster of galaxies in the initial stages of development. It is the most distant such grouping ever observed in the early universe.

In a random sky survey made in near-infrared light, Hubble found five tiny galaxies clustered together 13.1 billion light-years away. They are among the brightest galaxies at that epoch and very young — existing just 600 million years after the big bang.

Galaxy clusters are the largest structures in the universe, comprising hundreds to thousands of galaxies bound together by gravity. The developing cluster, or protocluster, is seen as it looked 13 billion years ago. Presumably, it has grown into one of today’s massive “galactic cities,” comparable to the nearby Virgo cluster of more than 2,000 galaxies.

“These galaxies formed during the earliest stages of galaxy assembly, when galaxies had just started to cluster together,” said Michele Trenti of the University of Colorado at Boulder and the Institute of Astronomy at the University of Cambridge in the United Kingdom. “The result confirms our theoretical understanding of the buildup of galaxy clusters. And, Hubble is just powerful enough to find the first examples of them at this distance.”

Full Story: http://hubblesite.org/newscenter/archive/releases/2012/05

Rare Ultra-Blue Stars Found in Andromeda’s Hub

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Credit: NASA; ESA; B. Williams and J. Dalcanton, University of Washington, Seattle

Credit: NASA; ESA; B. Williams and J. Dalcanton, University of Washington, Seattle

Peering deep inside the hub of the neighboring Andromeda galaxy, NASA’s Hubble Space Telescope has uncovered a large, rare population of hot, bright stars.

Blue is typically an indicator of hot, young stars. In this case, however, the stellar oddities are aging, sun-like stars that have prematurely cast off their outer layers of material, exposing their extremely blue-hot cores.

Astronomers were surprised when they spotted these stars because physical models show that only an unusual type of old star can be as hot and as bright in ultraviolet light. 

While Hubble has spied these ultra-blue stars before in Andromeda, the new observation covers a much broader area, revealing that these stellar misfits are scattered throughout the galaxy’s bustling center. Astronomers used Hubble’s Wide Field Camera 3 to find roughly 8,000 of the ultra-blue stars in a stellar census made in ultraviolet light, which traces the glow of the hottest stars. The study is part of the multi-year Panchromatic Hubble Andromeda Treasury survey to map stellar populations across the galaxy.

Full Story: http://www.nasa.gov/mission_pages/hubble/science/ultra-blue.html

Hubble Zooms In on Andromeda’s Double Nucleus

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Credit: NASA, ESA, and T. Lauer (National Optical Astronomy Observatory)

Credit: NASA, ESA, and T. Lauer (National Optical Astronomy Observatory)

A new Hubble Space Telescope image centers on the 100-million-solar-mass black hole at the hub of the neighboring spiral galaxy M31, or the Andromeda galaxy, the only galaxy outside the Milky Way visible to the naked eye and the only other giant galaxy in the local group.

This is the sharpest visible-light image ever made of the nucleus of an external galaxy.

The event horizon, the closest region around the black hole where light can still escape, is too small to be seen, but it lies near the middle of a compact cluster of blue stars at the center of the image. The compact cluster of blue stars is surrounded by the larger “double nucleus” of M31, discovered with the Hubble Space Telescope in 1992. The double nucleus is actually an elliptical ring of old reddish stars in orbit around the black hole but more distant than the blue stars. When the stars are at the farthest point in their orbit they move slower, like cars on a crowded freeway. This gives the illusion of a second nucleus.

Full Story: http://www.nasa.gov/mission_pages/hubble/science/double-nucleus.html

Largest Driver of Galaxy Growth Challenged

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A Hubble Space Telescope study of massive galaxies two to three billion years after the Big Bang has uncovered two remarkable results that challenge the common lore that major mergers play a dominant role in growing galaxies over a wide range of cosmic epochs.

Astronomers led by University of Texas at Austin graduate student Tim Weinzirl and associate professor Shardha Jogee will present their findings, recently published in The Astrophysical Journal, today at the 219th meeting of the American Astronomical Society in Austin.

Weinzirl and Jogee studied 166 of the most massive galaxies present only a few billion years after the Big Bang , selected from the GOODS NICMOS survey headed by professor Christopher Conselice of the University of Nottingham in the U.K.

Full Story: http://mcdonaldobservatory.org/news/releases/2012/JanAAS.html

VLBA, RXTE Team Up to Pinpoint Black Hole’s Outburst

January 11, 2012 Leave a comment

Astronomers have gained an important clue about a ubiquitous cosmic process by pinpointing the exact moment when gigantic “bullets” of fast-moving material were launched from the region surrounding a black hole. They made this breakthrough by using the ultra-sharp radio “vision” of the National Science Foundation’s Very Long Baseline Array (VLBA), along with NASA’s Rossi X-ray Timing Explorer (RXTE) satellite, to study an outburst from a system including a black hole and its companion star in 2009.

Black holes in such binary-star systems can pull material from their companions. That material forms a rapidly-rotating disk of material around the black hole, and “jets” of material are thrown outward perpendicular to the disk. Most of the time, the jets show a steady flow of material, but occasionally the steady jets disappear and superfast “bullets” of material are ejected at speeds approaching that of light. Such an outburst can produce as much energy in an hour as the Sun emits in five years.

Full Story: http://www.nrao.edu/pr/2012/diskjet/