High Quality Content by WIKIPEDIA articles! WASP-15b is an extrasolar planet discovered in 2008 by the SuperWASP collaboration, which seeks to discover exoplanets that transit their host stars. The planet orbits its host star at a distance of 0.05 AU every four days. The mass of this planet is about one half that of Jupiter, but its radius is nearly 50% larger than Jupiter`s, making the density of this planet only one quarter that of water; it is thought that some other form of heating must explain its extremely low density. WASP-15b`s discovery was published on April 29, 2009.