... A new class of exoplanet . Two groups discover planets with masses similar to Neptune's, unexpectedly bringing astronomers one step closer to finding Earth-size worlds around other stars. ... A stronomers announced today the first discovery of a new class of extrasolar planets far smaller than any previously detected around a Sun-like star. ... One of the new planets was discovered around a star already known to have three others, making this the first four-planet system identified so far. ...