PSR B1257+12

PSR B1257+12, previously designated PSR 1257+12, alternatively designated PSR J1300+1240, also named Lich, is a pulsar located 2300 light years from the Sun in the constellation of Virgo.

The pulsar has a planetary system with three known extrasolar planets, named "Draugr" (PSR B1257+12 A), "Poltergeist" (PSR B1257+12 B) and "Phobetor" (PSR B1257+12 C), respectively. They were both the first extrasolar planets and the first pulsar planets to be discovered; A and B in 1992 and C in 1994. A is the lowest mass planet yet discovered by any observational technique, with somewhat less than twice the mass of Earth's moon.

The convention that arose for designating pulsars was that of using the letters PSR (Pulsating Source of Radio) followed by the pulsar's right ascension and degrees of declination. The modern convention prefixes the older numbers with a B meaning the coordinates are for the 1950.0 epoch. All new pulsars have a J indicating 2000.0 coordinates and also have declination including minutes. Pulsars that were discovered before 1993 tend to retain their B names rather than use their J names, but all pulsars have a J name that provides more precise coordinates of its location in the sky.

On their discovery, the planets were designated PSR 1257+12 A, B, and C, ordered by increasing distance. They were discovered before the convention that extrasolar planets receive designations consisting of the star's name followed by lower-case Roman letters starting from "b", in order of discovery, was established. However, they are listed under the latter convention on astronomical databases such as SIMBAD and the Extrasolar Planets Encyclopedia, with A becoming b, B becoming c, and C becoming d.