January 27, 2011 — Astronomers have pushed NASA's Hubble Space Telescope to its limits by finding what is likely the most distant object ever seen in the universe. The object's light traveled 13.2 billion years to reach Hubble, roughly 150 million years longer than the previous record holder. The age of the universe is approximately 13.7 billion years.
The tiny, dim object is a compact galaxy of blue stars that existed 480 million years after the Big Bang. More than 100 such mini-galaxies would be needed to make up our Milky Way. The new research offers surprising evidence that the rate of star birth in the early universe grew dramatically, increasing by about a factor of 10 from 480 million years to 650 million years after the Big Bang.
"NASA continues to reach for new heights, and this latest Hubble discovery will deepen our understanding of the universe and benefit generations to come," said NASA Administrator Charles Bolden, who was the pilot of the space shuttle mission that carried Hubble to orbit. "We could only dream when we launched Hubble more than 20 years ago that it would have the ability to make these types of groundbreaking discoveries and rewrite textbooks."
Astronomers don't know exactly when the first stars appeared in the universe, but every step farther from Earth takes them deeper into the early formative years when stars and galaxies began to emerge in the aftermath of the big bang.
"These observations provide us with our best insights yet into the earlier primeval objects that have yet to be found," said Rychard Bouwens of the University of Leiden in the Netherlands. Bouwens and Garth Illingworth of the University of California at Santa Cruz reported the discovery in the January 27 issue of the British science journal Nature.
The object appears as a faint dot of starlight in the Hubble exposures. It is too young and too small to have the familiar spiral shape that is characteristic of galaxies in the local universe. Although its individual stars can't be resolved by Hubble, the evidence suggests this is a compact galaxy of hot stars formed more than 100-to-200 million years earlier from gas trapped in a pocket of dark matter.
"We're peering into an era where big changes are afoot," said Illingworth. "The rapid rate at which the star birth is changing tells us if we go a little further back in time we're going to see even more dramatic changes, closer to when the first galaxies were just starting to form."
The proto-galaxy is only visible at the farthest infrared wavelengths observable by Hubble. Observations of earlier times, when the first stars and galaxies were forming, will require Hubble's successor, the James Webb Space Telescope, scheduled to launch in 2014.
But the Associated Press reports that other astronomers have their doubts about this discovery.
Richard Ellis at the California Institute of Technology is troubled because Illingworth's team originally found three 13.2 billion-year-old galaxies and then withdrew that study. The authors then came up with an entirely different galaxy, so all that switching "makes it difficult to believe," he said.
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The farthest and one of the very earliest galaxies ever seen in the universe appears as a faint red blob in this ultra-deep–field exposure taken with NASA's Hubble Space Telescope. This is the deepest infrared image taken of the universe. Based on the object's color, astronomers believe it is 13.2 billion light-years away. (Credit: NASA, ESA, G. Illingworth (University of California, Santa Cruz), R. Bouwens (University of California, Santa Cruz, and Leiden University), and the HUDF09 Team)
This image of the Hubble Ultra-Deep Field is part of the deepest infrared image ever taken of the universe. The small blue box outlines the area where astronomers found what may be the most distant galaxy ever seen, 13.2 billion light-years away, meaning its light was emitted just 480 million years after the Big Bang. It is small and very faint and is shown separately in the larger box. Credit: NASA, ESA, Garth Illingworth (UC Santa Cruz), Rychard Bouwens (UC Santa Cruz and Leiden University) and the HUDF09 Team.
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