AUSTIN, TEX., JAN. 13 -- One night last spring, a young graduate student aimed a new instrument at a random patch of sky and found what appear to be primeval galaxies 17 billion light years away -- farther away and farther back in time than any objects previously observed.

That distance is about 95 percent of the way back to the time of the so-called Big Bang, the explosion believed to have created all matter and radiation in the universe. The finding is significantly older than the oldest previously sighted object, a quasar, announced just last month. Quasars are mysterious, star-like objects that emit powerful electromagnetic radiation.

The finding, if confirmed, will overturn leading theories of how galaxies form, astronomers said, since they appear to have formed much earlier than most theorists expected.

The student, Richard Elston, 27, was part of a team of University of Arizona astronomers who were the first to use an array of powerful infrared detectors, originally developed for the military, that is 4,000 times more sensitive and thus faster than previous instruments.

Astronomers use infrared instruments to study objects too faint to show up in the visible spectrum -- in this case up to 20,000 times fainter than the night sky.

The scientists have developed a kind of competition, which has accelerated in recent months, to find the most distant objects in the universe. Because distance in space also represents time, this means that the farthest objects existed the earliest.

In this case, the Arizona team thinks it has found two galaxies where primordial gaseous material is collapsing to form new stars -- 17 billion light years away.

Elston, who presented his finding at the 171st meeting of the American Astronomical Society, attended by more than 1,000 astronomers, cautioned that the team's findings are preliminary and require further study. Some astronomers at the meeting said the technique is so new it has not yet been calibrated at such vast distances.

However, Patrick J. McCarthy, a specialist in distant galaxies at the University of California at Berkeley, said it is a "very good bet" that Elston's conclusions are correct.

Hyron Spinrad, also of Berkeley, said that if confirmed, the findings are "pretty spectacular."

Steve Warren, of the Institute of Astronomy in Cambridge, England, who found the oldest quasar, said he would be convinced of the finding if a certain pattern appears in an analysis of the object's light emissions, plotted on a graph, that would confirm the distance. Such analysis "takes a lot of telescope time because the objects are so faint."

Astronomers judge an object's age and distance by measuring the wavelength of the light it emits. According to astronomical dogma, the older and more distant an object, the faster it is moving away from Earth. The faster it retreats, the more its light waves appear stretched, or shifted to the red end of the spectrum. This is called red shift.

The Arizona astronomers used a 61-inch telescope in the mountains north of Tucson, outfitted with a camera developed by a member of the observing team, Marcia Lebofsky Rieke. The camera's heart is a grid of heat-sensitive detectors arrayed on a one-eighth-inch square mercury-cadmium-telluride chip.

The array, containing more than 4,000 detectors, was supplied by the Rockwell International Science Center. The Arizona team's work was partly funded by the National Science Foundation and the National Aeronautics and Space Administration.

Elston said he made his discovery during a "shakedown" of the new infrared camera. "I ran it through the computer four times just to make sure it was what it appeared to be, and then I ran down the hall to tell the others. It was very exciting."

The team, focusing on a randomly selected patch of distant sky beyond the plane of the Milky Way galaxy, found two objects that were "very luminous, very red." They seemed to fit predictions of what galaxies should look like as they are forming, Elston said. When a galaxy of new stars is energetically aborning, theorists say, it goes through a short, 100-million-year phase of tremendous brightness, during which it might be visible to observers on Earth despite great distances.

Elston infers from his finding that if there are two such galaxies in the small patch he observed, they "must be everywhere" in the distant sky.

The objects Elston sighted seem to be at a red shift of more than 6, he said. Most galaxies are seen at a red shift of much less than 2, which, on some scales, indicates they are 13 billion light years away. Earth's galaxy is believed to be 10 to 12 billion years old, with the solar system forming within it about 5 billion years ago.