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. HAT-P-1 is an oddball planet, since it orbits...