User blog:Prakhar/Binary pulsar

binary pulsar A pulsar in orbit around a companion star-possibly a white dwarf, a neutron star, a low-mass star, or a supergiant. Astronomers generally learn about the exis tence of the companion star by the cyclical change that occurs in the pulse period of the pulsar as the two stars orbit each other. One of the most interesting classes of binary pul sars are the black widow pulsars-the first of which, called PSR 1957+20, was discovered in 1988. Intense radiation from a rapidly spinning millisecond pulsar causes material to evap from its stellar companion. For example, PSR 1957+20 has a spin rate of 0.0016 seconds and an orbital period of 9.2 hours. The PSR 1957+20 black widow pulsar's companion now has a remaining mass of just 0.02 solar masses. In about 25 million years or so this particular mil lisecond pulsar will have destroyed (that is, completely evap orated) its stellar companion and thereby become a solitary millisecond pulsar. Here on Earth female black widow spiders occasionally devour their male companions after mating, but that cannibalistic behavior appears to be the exception rather than the rule. Despite this somewhat inaccurate analogy with biology, astronomers continue to refer to this interesting class of binary millisecond pulsars that destroy (evaporate) their companion stars as black widow pulsars.