National Geographic : 2004 Dec
(Continuedfrom page 85) and rock near the edge of the solar system, but a similar planet closer to its star might resemble an oversize ver sion of Earth, with a rock surface. Or it might have an ocean hundreds of miles deep. "We can dream," says Queloz. So can Mayor and Queloz's competitors. Weeks before the Swiss team was sure of the Mu Arae discovery, two U.S. groups had quietly firmed up the case for other small worlds. Bar bara McArthur of the University of Texas's McDonald Observatory found a planet weigh ing as little as 14 Earth masses-as small as the Mu Arae find-racing around the star 55 Cancri every 2.8 days. Paul Butler and his colleagues added their own bantamweight, at 21 Earths. Now, at the Lick Observatory near San Jose, Cal ifornia, their group isbuilding a special-purpose telescope aimed at finding Neptune-size worlds far enough from their star to be habitable. Robotically controlled for efficiency, the 2.4 meter Automated Planet Finder will capture every glimmer of starlight with mirrors plated with silver instead of the usual aluminum. Next year Debra Fischer will set it to work inspecting a hundred stars night after night for hints of worlds compact enough that they just might host life on a solid surface or in a deep ocean. A planet as small as our own, however, will remain out of reach for both teams. That's because stars pulse and roil, creating surface motions that would make it impossible to detect a star's tiny drift-barely a crawl-under the spell of an Earth. But there are other ways to parse starlight for hints of real Earths. , Forty years ago William Borucki helped design heat shields for the Apollo moon missions. Not far from his office at NASA's Ames Research Center near San Jose, parachutes for the Mars landings in January were tested in the silvery wind tunnels that run between buildings like oversize air ducts. But Borucki's ambitions have vaulted far beyond the solar system. At an age when many people think about retirement, he's planning a four-year, 400-million-dollar space mission to hunt for Earth-size planets. The searchfor planets aroundotherstarsis a marchtoward devices able to capture the light of an Earth size planet. Modest telescopes were enough to indirectly detect the first planets, gas giants about the size of Jupiter.But actually making an image of an alien giant requires powerful instruments attached to the biggest telescopes, like the Kecks in Hawaii and the Very Large Telescope in Chile (below) actually four huge telescopes plus smaller, movable scopes that can merge their light for a sharper view. Starting in 2007, a series of space missions may realize the ultimate goal of finding other Earths.