Black Widow Pulsar

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Black Widow Pulsar
B1957 comp.jpg
The blue and green are optical images of the field in which the black widow pulsar is found, the green indicating the H-alpha bow shock. The red and white are secondary shock structures discovered in x-ray by the Chandra X-ray Observatory.
Observation data
Epoch J2000      Equinox J2000
Constellation Sagitta
Right ascension 19h 59m 36.77s
Declination +20° 48' 15.12"
Apparent magnitude (V) 20.4
B−V color index 0
Rotation1.60734 ms
Other designations
QX Sge, PSR J1959+2048, PSR B1957+20
Database references

The Black Widow Pulsar (PSR B1957+20) is an eclipsing binary millisecond pulsar in the Milky Way. Discovered in 1988, it is located roughly 6,500 light-years away from Earth. It orbits with a brown dwarf or Super-Jupiter companion with a period of 9.2 hours with an eclipse duration of approximately 20 minutes. When it was discovered it was the first such pulsar known.[1] The prevailing theoretical explanation for the system implied that the companion is being destroyed by the strong powerful outflows, or winds, of high-energy particles caused by the neutron star, and so the sobriquet black widow was applied to the object. Subsequent to this, other objects with similar features have been discovered, and the name has been applied to the class of millisecond pulsars with an ablating companion.

Later observations of the object showed a bow shock in H-alpha and a smaller-in-extent shock seen in X-rays (as observed by the Chandra Space Telescope), indicating a forward velocity of approximately a million kilometers per hour.[2]

In 2010 it was estimated that the neutron star's mass was at least , and possibly as high as (the latter of which, if true, would surpass PSR J0740+6620 for the title of most massive neutron star yet detected, and place it within range of the Tolman–Oppenheimer–Volkoff limit).[3]


The pulsar has a substellar companion, possibly a brown dwarf.

The Black Widow Pulsar planetary system[4]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b 22 MJ 0.38


Artist impressions of the Black Widow Pulsar.

See also[edit]


  1. ^ Fruchter, A. S.; Stinebring, D. R.; Taylor, J. H. (1988). "A millisecond pulsar in an eclipsing binary". Nature. 333 (6170): 237–9. Bibcode:1988Natur.333..237F. doi:10.1038/333237a0. S2CID 4337525.
  2. ^ Chandra X-Ray Observatory data for B1957+20 "[1]"
  3. ^ Van Kerkwijk, M. H.; Breton, R. P.; Kulkarni, S. R. (2011). "Evidence for a Massive Neutron Star from a Radial-Velocity Study of the Companion to the Black-Widow Pulsar Psr B1957+20". The Astrophysical Journal. 728 (2): 95. arXiv:1009.5427. Bibcode:2011ApJ...728...95V. doi:10.1088/0004-637X/728/2/95. S2CID 37759376.
  4. ^ "The Extrasolar Planet Encyclopaedia — PSR B1957+20 b". Retrieved 2021-01-18.