Slew of distant galaxies tells a cosmic tale.

On images packed with celestial objects, distant galaxies look no different from the faint smudge of common, nearby galaxies. Yet these bodies lie several billion light-years from Earth and reveal what the universe was like at a much earlier age.

As recently as a year ago, astronomers had no proven method of picking out distant galaxies from the crowd. Now, researchers have spied a flood of faraway objects, aset of findings that could revolutionize cosmology.

Using a criterion based on an object's color, researchers early this year announced that they had identified 23 galaxies so distant from Earth that their light has taken 85 percent of the age of the universe to reach us (SN: 2/24/96, p. 120). Since then, the same team, which includes Charles C. Steidel of the California Institute of Technology in Pasadena and Mark E. Dickinson of the Space Telescope Science Institute in Baltimore, has established that at least 47 more galaxies are just as distant. Using a similar technique, another group, which includes James D. Lowenthal and Sandra M. Faber of the University of California, Santa Cruz, has found an additional 12 objects at similar distances. Thus, in a single year astronomers have detected about 80 galaxies that date from an extremely ancient era.

Astronomers estimate a galaxy's distance by using spectroscopy to measure its redshift, the amount by which the expansion of the universe shifts light to longer, or redder, wavelengths. The 80 galaxies have redshifts of about 3.

Another 400 galaxies have colors that make them likely candidates, although researchers have yet to measure their redshifts.

Piero Madau of the Space Telescope Science Institute and his collaborators, including Dickinson, have now gone a step further. Adapting their color criterion to find objects that are even more distant, the team has identified 14 galaxies seen by the Hubble Space Telescope that may have redshifts around 4. This redshift corresponds to an era when the universe was only 9 percent of its present age.

Dickinson reported the findings last month at a conference in Baltimore.

Madau's team provides further details in an article accepted for publication in the Monthly Notices of the Royal Astronomical Society. Dickinson cautions that because all 14 objects are extremely faint, recent observations have succeeded in collecting the necessary spectral data for only one of the galaxies, which appears to have a redshift of 4.02. Nonetheless, the findings help lay down rules about star formation and the evolution of galaxies, says Madau. "It's no longer [just] a case of finding more and more distant galaxies," adds Dickinson. "We can now use the objects to make meaningful statements about physical processes in the cosmos."

In comparing the density and luminosity of galaxies at different times in the cosmos, Madau's team finds that star formation proceeded slowly. The researchers see no evidence that a wave of star birth set all the earliest galaxies ablaze at once. They also confirm earlier evidence that star formation peaked when the universe was one-third of its present age. As the astronomers look at progressively earlier times, they find fewer galaxies, suggesting that they may soon encounter the epoch when the first galaxies assembled.