'BoRG' Survey Spots Ancient Cluster of Baby Galaxies: Big Pic

Jan. 13, 2012 -- Galactic clusters are the largest structures in the Universe. Spanning millions of light-years, they are groupings of galaxies connected to each other by gravity and moving inexorably outwards together within our ever-expanding universe.

Our own galaxy is part of a cluster known as the Local Group, which contains at least 45 individual galaxies. It takes time for galaxies to organize into groups like this, and while it's not known exactly how long this process may take astronomers now have a new piece for the puzzle.

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A team of researchers using infrared data from Hubble's Wide Field Camera 3 have located five small and incredibly distant galaxies that appear to be bound together gravitationally, making this the furthest galactic cluster ever seen. Located 13.1 billion light-years away, this protocluster appears as it did only 600 million years after the birth of the universe.

The individual galaxies are much smaller than our own (one-half to one-tenth the size) and can only be detected in near-infrared, as their light has been stretched beyond the visible spectrum due to their sheer distance.

The discovery was made during a random sky search, part of the Brightest of Reionizing Galaxies (BoRG) survey which scans the sky in near-infrared, attempting to locate distant sources of energy. The image above circles the locations of the five galaxies within a visible light image of the surrounding region while the individual galaxies are shown down the right side in infrared.

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The team, led by Michele Trenti of the University of Colorado at Boulder and the Institute of Astronomy at the University of Cambridge in the UK, has been faced with quite a challenge because of the dimness of these distant objects. Locating them is a "hit-and-miss" process.

"We need to look in many different areas because the odds of finding something this rare are very small," said Trenti. "Typically, a region has nothing, but if we hit the right spot, we can find multiple galaxies."

Since these young galaxies are seen as they were over 13 billion years ago, it's assumed they have long since gathered together to form one of the giant modern "galactic city" clusters we see today... such as the nearby Virgo cluster which now contains over 2,000 galaxies.

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More observations will be needed to determine if these new-found galaxies are indeed bound together gravitationally.

This research was presented at this week's American Astronomical Society's meeting in Austin. The full report will be published in The Astrophysical Journal. Read the news release here.

--by Jason Major

Image credit: NASA, ESA, M. Trenti (University of Colorado, Boulder, and Institute of Astronomy, University of Cambridge, UK), L. Bradley (STScI), and the BoRG team