Imagine a planet nearly twice the diameter of giant Jupiter, yet puffy enough to float on water. Discovered by a team led by Georgi Mandushev of the Lowell Observatory in Flagstaff, Ariz., this alien orb is both the largest and the lowest-density planet yet found in the cosmos.
As seen from Earth, the planet periodically passes in front of its parent star, blocking about 1 percent of the starlight.