for National Geographic News
Twenty-eight new planets have been discovered outside the solar system in the past year, scientists announced yesterday.
The new discoveries raise the total number of exoplanets—worlds that circle other stars—to 236.
Many of the discoveries were published in scientific journals over the past year.
Monday's announcement at a meeting of the American Astronomical Society in Honolulu, Hawaii, was the first time the finds were presented together to the public.
Most of the new planets are probably huge balls of gas, more like Jupiter than Earth.
But scientists say the increasing rate at which they're finding new exoplanets makes it almost certain that the galaxy is swarming with smaller, rocky, and potentially habitable worlds that have so far eluded detection.
(Related: "Many 'Earths' Are Out There, Study Says" [April 6, 2005].)
"We're finally now getting a sense that our solar system is not a rarity," said Geoff Marcy, who led the California and Carnegie Planet Search team that made many of the discoveries.
"There are indeed tens of billions of planetary systems out there, no doubt some of them rocky Earths, lukewarm, and suitable for life."
Marcy, an astrophysicist at the University of California, Berkeley, spoke to National Geographic News from the Keck Observatory atop Hawaii's Mauna Kea, where many of the new exoplanets were first spotted.
Because exoplanets are too far away to be seen directly, the 28 new planets were discovered by looking for the so-called Doppler wobble among stars.
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