The first solid evidence for an exoplanet (extrasolar planet) came in 1992 when scientists calculated that two bodies must be orbiting the pulsar PSR 1257. Pulsars are rapidly spinning neutron stars (the superdense remnants of massive stars that have exploded as supernovae), which emit radio waves in pulses. Researchers think the two planets are the leftover rocky cores of gas giants whose atmospheres were completely blown away in the prior supernova event or they may have formed in a second round of planet formation after the supernova.

Exoplanet Names: PSR 1257 b and PSR 1257 c
Star/Constellation Name: PSR 1257/Virgo
Distance from Earth: 978 light-years (One light-year equals the distance light in a vacuum travels in a year: 5.88 trillion miles, or 9.46 trillion kilometers.)
Exoplanet Mass: 4.1, 3.8 Earths (0.013 and 0.012 Jupiter)
Distance from Host Star: 0.36, 0.46 AU (An AU, or astronomical unit, is the average distance between Earth and the sun, which is about 93 million miles, or 150.6 million kilometers.)
Year Discovered: 1991