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The Edge of Space
30 December 1998 5:00 pm
Astronomers from the State University of New York, Stony Brook, have won a race to the edge of the universe. After 3 weeks of working around the clock on infrared data from the Hubble Space Telescope, they may have shattered previous records for the most distant stars and galaxies, pushing the frontier of the visible universe to distances so great that they are seen just a few hundred million years after the big bang. "We knew other groups were working on the same data," says one of the astronomers, Ken Lanzetta, "so there was a lot of hurry."
Together with his Stony Brook colleague Amos Yahil and others, Lanzetta analyzed data from a very small patch of sky in the southern constellation Tucana, where the Hubble gathered light for 10 straight days last October. NASA released data from this observation, called Hubble Deep Field South, on 23 November. By 18 December, the team had published its results on the Internet: a catalogue of 323 distant galaxy candidates, along with their redshifts--a measure of distance and, hence, age.
Lanzetta and Yahil claim to have found 14 galaxies with redshifts between 5 and 10, and another five candidates with redshifts larger than 10--almost twice the previous record holder of 5.64. At a redshift of 10, galaxies are seen when the universe was only 9% of its current size and probably just a few hundred million years old. "We are getting back to a significant fraction of the age of the universe," says Yahil. If he and Lanzetta are right, galaxies and stars formed much earlier in cosmic history than most theorists had imagined.
There is a catch, however. Because the galaxies are extremely faint, Lanzetta and Yahil deduced redshifts with "photometric" techniques that are considered less reliable than traditional spectrum measurements. "You have to have a lot of faith at these high redshifts," says Charles Steidel of the California Institute of Technology in Pasadena, who pioneered the photometric redshift technique a few years ago.