For those of us who still mourn the demise of the “Star Trek” franchise and its vision of the cosmos as a thrillingly multicultural if occasionally lethal nightclub, the announcement last week that many Sun-size stars in our galaxy are girdled with Earth-size planets was, frankly, transporting.
The newly detected worlds are far too close to their stellar parents to have much chance of harboring even microbial life, let alone anybody capable of looking boss in spandex. Nevertheless, the discovery gave astronomers and alien life-seekers heart. For one thing, the planets are encouragingly compact. In the past decade, astronomers have found some 250 extrasolar planets, but most have been forbiddingly Jovian: celestial gas bags presumed to have no solid surface and hundreds of times the mass of Earth. In the new report, Michel Mayor of the Geneva Observatory and his colleagues said they had found 45 planets that were only a few times as massive as our beloved blue base, which means that they, like Earth, are probably built of rock.
The tally is proportionally impressive as well: roughly one in three stars surveyed showed signs of harboring stony planets, and other researchers performing similar studies said the figure might be more like one in two. And though the 45 planets on the Geneva list are all “star-huggers,” as one astronomer put it, with orbital periods of 2 to 50 days — even Mercury needs nearly three months to circumnavigate the Sun — researchers are confident that other rocky planets remain to be found at Earthier distances from their suns.
Sara Seager, a planetary theorist at the Massachusetts Institute of Technology, said astronomers hunt for planets by detecting telltale wobbles they induce in their host stars, a method that selectively nets the too big or too near. Nevertheless, she said, “the fact is, as soon as astronomers started looking for low-mass planets, they found a whole bunch, and that’s a real breakthrough.” Just imagine the orgy of moderation that a more inclusive scan would reveal.
http://www.nytimes.com/2008/06/24/science/24angi.html?th&emc=th