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Astronomers have detected a galaxy located 13 billion light-years from Earth, making it the most distant such object on record. The find, described in a paper to be published in the Astrophysical Journal, should help scientists better understand the so-called cosmic Dark Ages, when the universe¿s first galaxies and quasars transformed opaque hydrogen into the transparent cosmos that exists today.
The record-breaking galaxy is so far away and so dim that the astronomers needed considerable help to observe it. The galaxy cluster known as Abell 2218, which is very massive and located between the galaxy and Earth, bent and magnified its light. "As we were searching for distant galaxies magnified by Abell 2218, we detected a pair of strikingly similar images whose arrangement and color indicate a very distant object," explains lead author Jean-Paul Kneib of the California Institute of Technology. The data collected by NASA¿s Hubble Space Telescope and the W. M. Keck Telescopes in Hawaii signal that the object¿s redshift, which measures the shift of light to longer wavelengths and reveals its distance from Earth, lies between 6.6 and 7.1. "The galaxy we have discovered is extremely faint, and verifying its distance has been an extraordinarily challenging adventure," says Kneib. "Without the 25 times magnification afforded by the foreground cluster, this early object could simply not have been identified or studied in any detail at all with the present telescopes available."
The galaxy, measuring just 2,000 light-years across, is a fraction of the size of our own Milky Way, which stretches 100,000 light-years in diameter. The researchers posit that the galaxy is churning out stars quite rapidly, manufacturing stellar masses each year equivalent to almost three suns. "Estimating the abundance and characteristic properties of sources at early times is particularly important in understanding how the universe reionized itself, thus ending the Dark Ages," remarks study co-author Mike Santos of the Institute of Astronomy in Cambridge, England. "The cosmic lens has given us a first glimpse into this important epoch."
