PSR B125712

PSR B1257+12 is a millisecond pulsar located 2300 light-years away in the constellation Virgo. It was discovered in 1992 by astronomer Aleksander Wolszczan and later confirmed to be orbited by two planets, making it the first known planetary system outside the Solar System. A third planet was identified in 1994, bringing the total to three: Draugr (A), Poltergeist (B), and Phobetor (C). These planets were named after mythological beings due to their unusual nature.

The pulsar is characterized by a mass of 1.4 solar masses, a radius of about 10 kilometers, and a surface temperature of approximately 28,856 K. It formed from the merger of two white dwarfs, which left behind a rapidly spinning neutron star surrounded by debris that likely reformed into planets.

The system's formation is unique, as it was believed to result from a white dwarf–white dwarf merger followed by the collapse into a pulsar and subsequent planetary formation. The initial discovery of the first two planets in 1992 surprised astronomers who expected planets only around main-sequence stars. Subsequent claims of a fourth planet were retracted after further analysis showed they could be explained by changes in the pulsar's dispersion measure.

This system remains one of the few known examples of planetary systems orbiting a pulsar, with only five others confirmed to date. The PSR B1257+12 system continues to be a subject of study for understanding extreme astrophysical phenomena and planetary formation under unique conditions.