Nasa uncovers hundreds of young galaxies
Friday, 22 Sep 2006 13:18
Distant early galaxies detected by Hubble
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Scientists have uncovered hundreds of young galaxies that existed 13 billion years ago.
Discovered by Nasa's Hubble telescope, the gold mine of over 500 galaxies is said to represent the most comprehensive compilation of galaxies in the early universe.
Existing less than a billion years after the Big Bang, the galaxies are particularly significant as a decade ago early galaxy formation had not been studied in depth and no galaxies existing at such an early stage had been spotted.
The newly-discovered galaxies are bluish in colour, indicating that star birth is taking place. However the images appear red because of their vast distance from the Earth. The light from them took nearly 13 billion years to reach the Earth, causing the blue light to shift to red due to the expansion of space.
Rychard Bouwens of the University of California, who led the Hubble study, said: "Finding so many of these dwarf galaxies, but so few bright ones, is evidence for galaxies building up from small pieces – merging together as predicted by the hierarchical theory of galaxy formation."
Astronomers have debated whether the hottest stars in early-forming galaxies could have provided enough radiation to heat the cold hydrogen gas between galaxies in the early universe.
The latest pictures from the Hubble telescope are argued to have answered this question, as study co-author Garth Illingworth of the University of California said: "Seeing all of these starburst galaxies provides evidence that there were enough galaxies one billion years after the Big Bang to finish reheating the universe.
"It highlights a period of fundamental change in the universe, and we are seeing the galaxy population that brought about that change."
Hubble's findings will be published in the November 20th issue of the Astrophysical Journal.
The discovery of the galaxies is said to provide evidence that many more exist. Hubble's anticipated upgrade with the Wide Field Planetary Camera 3 and the James Webb Space Telescope are thought to be able to detect more galaxies at even greater distances in the future.