Cosmic ray mystery lifted in new findings Cosmic rays -- fast-moving particles that constantly pummel our planet -- come from the explosion of supernovae, new research confirmed Thursday, resolving an astronomical mystery.
15 February 2013
'17 billion' Earth-sized planets in Milky Way: study The Milky Way contains at least 17 billion planets the size of Earth, and likely many more, according to a study out Monday that raises the chances of discovering a sister planet to ours.