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While some astronomers searched for planets, others tried to detect intelligent alien life directly. In 1960, astronomer Frank Drake started Project Ozma, an attempt to look seriously for radio signals from alien civilizations. It was the first in what became a series of experiments in seti, the Search for Extra-Terrestrial Intelligence. Several are still going on, but so far without success.

The race to discover planets around sunlike stars proved similarly fruitless until about 18 months ago. At the time, Marcy and Butler were sure they had the inside track on finding them. The telescope they use, at Lick Observatory in the mountains above California's Silicon Valley, has an excellent view of the heavens. It also has one of the world's finest spectrometers. After a major refurbishment in November 1994, the device was even better. In principle, says Marcy, "we could detect not just Jupiters but Saturns."

In principle, maybe, but in practice there are dozens of factors that can confuse matters. For example, stars, including the sun, pulse rhythmically with waves generated deep in their interiors, making the surface bulge toward and sink away from the Earth just as though the whole star were wobbling. Stars can also have huge blotches--sunspots, in essence--that change the mix of colors as they rotate into and out of view. And spectrometers are subject to all sorts of errors that come from changes in temperature and electronic glitches. Thus, Marcy and Butler had to run their observations through a sophisticated computer program they'd written to sort useful from useless information--a piece of software so complex and so demanding of computer time that their colleagues kidded them that it would never work.

They were wrong. As it happened, Butler was in the middle of rewriting the software last October to accommodate the spectrometer's newly heightened sensitivity when a disconcerting flood of E-mail started pouring in. Michel Mayor and Didier Queloz, of the Geneva Observatory in Switzerland, had just detected a planet circling the star 51 Pegasi, lying 45 light-years away in the constellation Pegasus. Says Queloz: "We first thought that our instrument was faulty, but repeated verifications and computations finally convinced us that we had bagged a planet."

More than one astronomical discovery has disappeared on a closer look, though, so Marcy and Butler headed for the telescope, determined either to debunk or verify the Swiss team's claims. Sure enough, says Marcy, after four nights at Lick and many hours of computer time, "everything they'd said about the planet was confirmed." (Butler and Marcy did, however, show that hints the Swiss team had found a second planet around the same star were mistaken.)

The object turned out to be peculiar. It's half as massive as Jupiter, but orbiting closer to 51 Pegasi than Mercury is to the sun. That means its surface temperature is 1300ûC, hotter than a blast furnace. Still, it is a planet. "I was a little schizophrenic about it," says Marcy. "On the one hand, we had been scooped. But I also felt euphoric that humanity had entered a new era in which new worlds were going to be subject to exploration."

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