Black Widow Pulsar

The Black Widow Pulsar (B1957+20, PSR B1957+20, or PSR J1959+2048) is a binary star consisting of a pulsar (neutron star) and a companion in an orbit that eclipses the pulsar. This has allowed for unique observations on the effect of the companion's "atmosphere" on the pulsar signal.

The name comes from the fact that the neutron star appears to be evaporating the companion, which could disappear in a billion years or so, and the phrase black widow pulsar has been adopted for pulsars that are doing this. The companion has been thought to be a white dwarf, but is now considered a brown dwarf or giant extra-solar planet. Though it might currently have a mass indicating a planet, it is thought to be the stellar remnant.

The name black widow pulsar has become a pulsar classification term as analogous characteristics of other pulsars have been discovered, e.g., for PSR J1301+0833.