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Astronomers have found a surprisingly heavy early galaxy, according to a new report. Data from two NASA telescopes have revealed the presence of a galaxy that had eight times the mass of our own Milky Way when it was less than a billion years old. "This galaxy appears to have 'bulked up' amazingly quickly, within the first few hundred million years after the big bang," remarks team member Bahram Mobasher of the Space Telescope Science Institute and the European Space Agency.
Astronomers used the Spitzer and Hubble Space Telescopes to take an inventory of very distant galaxies. Within the region of sky known as the Hubble Ultra Deep Field, which contains nearly 10,000 galaxies, one known as HUDF-JD2 stood out. The light coming from it originated when the universe was about 800 million years old and indicates that the stars within it are heftier than expected. "This would be quite a big galaxy, even today," says Mark Dickinson of the National Optical Astronomy Observatory. "At a time when the universe was only 800 million years old, it's positively gigantic." The researchers describe the find in papers slated for publication in the November and December issues of the Astrophysical Journal.
The discovery, together with recent findings of mature stars in other early but less massive galaxies, may force astronomers to reconsider theories of general galatic formation. The planned launch (after June 2013) of the James Webb Space Telescope, armed with light-collecting power to see even more distant objects, should help further unravel the mystery.