Farthest Galaxy Protocluster Discovered By Hubble
January 10, 2012

Farthest Galaxy Protocluster Discovered By Hubble

Thanks to the Hubble Space Telescope, a team of astronomers have located the most distant grouping of still-developing galaxies ever witnessed in the early universe, NASA announced on Tuesday.

According to the U.S. space agency, Hubble found a cluster of five tiny galaxies located 13.1 billion light years away during a random sky survey conducted in near-infrared light.

The galaxies in the developing cluster, or protocluster, are said to be among the brightest at that epoch and were "very young -- existing just 600 million years after the big bang," NASA said in their media advisory.

"These galaxies formed during the earliest stages of galaxy assembly, when galaxies had just started to cluster together," study leader Michele Trenti, a research associate at the University of Colorado at Boulder (CU-Boulder) and a recently appointed scientist at the Institute of Astronomy at the University of Cambridge, said in a statement.

"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," he added.

According to the researchers, galaxy clusters consist of hundreds to thousands of individual galaxies held together by gravity, and are the largest structures in the universe. Over the past 13 billion years, they believe that the recently observed protocluster has since grown into one of the most massive of all clusters, noting that they believe it is comparable in mass to the 2000-plus galaxy large Virgo cluster.

Trenti and his colleagues were scheduled to present their findings Tuesday at the American Astronomical Society meeting in Austin, Texas. Their study will also be published in a future issue of The Astrophysical Journal.

"Records are always exciting, and this is the earliest and the most distant developing galaxy cluster that has ever been seen," said Michael Shull, a professor at the CU-Boulder astrophysical and planetary sciences department and a member of the team who discovered the protocluster. "We have seen individual galaxies this old and far away, but we have not seen groups of them in the construction process before."

"The five bright galaxies spotted by Hubble are about one-half to one-tenth the size of our Milky Way, yet are comparable in brightness," NASA reported. "The galaxies are bright and massive because they are being fed large amounts of gas through mergers with other galaxies. The team's simulations show that the galaxies eventually will merge and form the brightest central galaxy in the cluster."

The observations were part of the Brightest Reionizing Galaxies survey, they added.

Joining Trenti and Shull on the study were other researchers from the University of Colorado, the University of California - Santa Cruz, UCLA, the University of Leiden in the Netherlands, the University of Kentucky, ETH Zurich in Switzerland, and the Space Telescope Science Institute. The Hubble Space Telescope used in the discovery is a joint project of NASA and the European Space Agency (ESA).


Image Caption: The composite image taken in visible and near-infrared light, reveals the location of five tiny galaxies clustered together 13.1 billion light-years away. The circles pinpoint the galaxies. Credit: NASA, ESA, M. Trenti (University of Colorado, Boulder and Institute of Astronomy, University of Cambridge, U.K.), L. Bradley (Space Telescope Science Institute, Baltimore), and the BoRG team


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