Astronomers find distant, fluffy planet

WASHINGTON - The largest planet ever found orbiting another star is so puffy it would float on water, astronomers said Thursday. The newly discovered planet, dubbed HAT-P-1, is both the largest and least dense of the nearly 200 worlds astronomers have found outside our own solar system.

HAT-P-1 orbits one of a pair of stars in the constellation Lacerta, about 450 light-years from Earth.

"This new planet, if you could imagine putting it in a cosmic water glass, it would float," said Robert Noyes, a research astrophysicist with the Smithsonian Astrophysical Observatory. The planet, a gas giant, is probably a puffed up ball of hydrogen and helium.

HAT-P-1 is an oddball planet, since it orbits its parent star at just one-twentieth of the distance that separates Earth from our own sun. While Earth takes a year to orbit the sun, the newly found planet whips around its star once every 4.5 days.

Astronomers believe HAT-P-1 may belong to an entirely new class of planets, along with a second, smaller distant world that's also puffier than theories would have predicted, Noyes said.

Astronomers used a network of telescopes in Arizona and Hawaii to discover the planet. Its parent star is too faint to see with the naked eye but can be spied with binoculars.

On the Net: Harvard-Smithsonian Center for Astrophysics: http://www.cfa.harvard.edu/
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