Astronomers have discovered what may be the largest planet yet found—an orb that's 36 percent wider than Jupiter and that circles a nearby star. Researchers say that they're baffled by the giant extrasolar body, which has the lowest density of any known planet.
Half as massive as Jupiter and residing 450 light-years from Earth, the planet is just one-twentieth the distance from its parent star that Earth is from the sun. But the planet's presence in this hot zone isn't enough to explain the orb's low density, about one-quarter that of water, says codiscoverer Robert Noyes of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. Many other extrasolar planets l