Three planets orbit the dead star PSR B1257+12 in this artist's concept. The dead star is a pulsar, which an extremely dense neutron star that spins rapidly, beaming energy into space. The pulsar formed when a massive star exploded as a supernova. The planets, which were the first comfirmed worlds detected outside our solar system, probably formed from debris from the exploded star and its original system of planets and other material. The discovery was announced in January 1992. [NASA/JPL]