Beyond Hubble

PHOTO COMPOSITE BY THE GEMINI OBSERVATORY
ALMOST HEAVEN: The dome of Gemini North sits perched under a brilliantly clear sky 14,000 ft. above sea level on Hawaii's Mauna Kea

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"People argued at the time that it would be crazy to rely on computers because they might fail," recalls Mountain, whose Gemini telescopes in Hawaii and Chile were built on the European model. "But when you think about it, planes are controlled by onboard computers, and those computers essentially never fail."

Neither do the ones that run the telescopes. The European Southern Observatory's New Technology Telescope, built in the 1980s as a 3.5-m precursor to the Very Large Telescope (VLT), worked beautifully. So did Keck 1 when it went into operation in 1992. And so, in turn, have the other big telescopes as they've come online over the past two years. With both enormous size and smooth performance, these giant telescopes are doing science on a heroic scale--especially the Keck, which has had more than a half-decade head start on its rivals. In fact, says an astronomer who prefers to remain anonymous lest his outspoken views earn him professional enemies, "the Keck has done way more science over its lifetime than the Hubble."

He may be right. The Hubble's forte is taking brilliantly sharp pictures. But the real meat of astronomical discovery comes not so much in pretty photos of celestial objects but in the detailed analysis of their light. By smearing that light into a spectrum--the rainbow of its component colors--scientists can identify the chemical makeup of a star or galaxy, how far away it is and how fast it's rotating, among other data. If the image of a star is going to be smeared anyway, sharp pictures don't matter much, so ground-based telescopes are at no disadvantage.

So while the Hubble is good at locating faint celestial objects, the follow-up science is often done by observatories on the ground. In essence, the Hubble is like the small finder telescopes backyard astronomers use to pinpoint interesting objects for their full-size telescopes.

In many cases, though, the ground-based giants can find their own way through the universe. Geoff Marcy, for example, leader of the world's most prolific planet-hunting team, began his research at the relatively modest 3.5-m telescope at Lick Observatory in California. Then, in 1996, he moved most of his project to the Keck, with dramatic results. "We've discovered 35 planets orbiting sunlike stars so far," says Marcy, who holds joint appointments at the University of California, Berkeley, and San Francisco State University. "And the majority of them have been with the Keck."

The objects Marcy looks at aren't especially faint: he and his collaborators find planets by looking for stars that wobble under the gravitational tug of unseen companions. But the wobbles are so subtle that a lesser telescope can barely detect them. "With a 10-m telescope," says Marcy, "we can look at fainter stars and pick out the signature of smaller objects."

Indeed, Marcy announced last year that he'd found a planet the size of Saturn--the smallest yet discovered. "We think we can get down to the level of Neptunes," he says, "which are only 10 times as massive as Earth." Despite having so many planets in hand, Marcy and other astronomers haven't found anything like our home solar system: most of the planets found elsewhere are not only huge, but they career around in orbits that would fling smaller, Earth-like planets out into space--a discouraging start to the search for life in the galaxy, though it's far too early to give up.

George Djorgovski is using the Keck as well, but where Marcy's quarries are no more than 200 light-years way, Djorgovski's are closer to 10 billion. A professor at Caltech, Djorgovski has lately been concentrating on gamma-ray bursts--mysterious flashes of high-energy radiation that have baffled astronomers for nearly 40 years. If these blips of electromagnetic energy can be seen from far across the universe, as some astronomers believe, then they must briefly shine as bright as the rest of the stars in the universe put together--a seemingly preposterous assertion.

But in 1998, Djorgovski and his colleagues used the Keck to take visible-light pictures of a burst first spotted by the Compton Gamma Ray Observer satellite--and sure enough, it came from billions of light-years away. To date, the best explanation theorists have come up with is that the bursts come from "hypernovas," massive stars exploding with hitherto unsuspected power. "I feel really fortunate," says Djorgovski. "This was a world-class mystery, and the Keck allowed us to help solve it."