Telltale Stars

Finding the oldest galaxies

They look like faint, random smudges on a photographic plate. But for scientists these markings hold a world of meaning. Last week University of California Astronomer Hyron Spinrad and his colleagues announced that the blurs represent four galaxies, great elliptical collections of stars, perhaps even larger than our own Milky Way. More astonishing, they are some 2 billion light-years farther off in space than any other galaxy ever discerned by telescope.

The observations came from the 120-in. reflector at the University of California's Lick Observatory, enhanced by computer technology. To study such extremely faint objects, astronomers had to focus their light onto a photo-imaging tube akin to the night-vision devices used by the military in Viet Nam. This electronic gadgetry strengthens the signals and then stores them as electronic data in a computer, while it subtracts any disturbing background glare. Eventually the astronomers accumulated enough light to produce spectra, or light signatures, for all four galaxies, but that took considerable doing. The image of just one of the galaxies, known as 3C 427.1, required 40 hours of telescope time on 23 separate nights over a period of three years.

The scientists' patience was amply rewarded. The wave lengths of celestial light had been drastically stretched, or shifted to the red end of the spectrum--an effect comparable to a familiar terrestrial one: the lowering of a horn's pitch as a car speeds away from an observer. From that yardstick, the astronomers calculated that the galaxies were receding from earth at more than half the speed of light, or better than 93,000 miles per sec. Since objects with higher velocities are presumed to be more distant in a universe that seems to be expanding at a uniform rate, scientists figured the galaxies were about 10 billion light-years away. That meant they were at least 10 billion years old.

Some quasars have even larger red shifts and perhaps are older and more distant. But quasars, which resemble stars in some ways and in some ways do not, are still so puzzling that astronomers prefer to turn to more familiar phenomena, like galaxies, in their explorations of the universe's evolution. The newly discovered galaxies, in fact, should be especially good time machines. Their light is much less bright than might be expected from a young galaxy. Astronomers speculate that the newfound galaxies may already have been 6 billion years old when the light left them, and thus could have been formed 16 billion years ago. That would date their creation only 2 billion years or so after the Big Bang, the great explosion in which, most astronomers believe, the universe was born.

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