Powerful winds and radiation from a pulsar (bright dot at center of green and purple cones) heat and erode a companion star in this artist's concept. Over time, this process may completely evaporate the companion. The pulsar spins rapidly, emitting beams of energy (the colored cones) that can be seen from Earth as pulses of energy. [NASA/GSFC/Cruz deWilde]
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Black Widow Pulsars
Black widows lurk among the stars. They slowly destroy their companions, ingesting part and sweeping away the remains.
These nasty-sounding objects are pulsars — the spinning corpses of once-mighty stars that blasted themselves apart. All that’s left is their crushed cores, known as neutron stars. Some neutron stars spin, emitting beams of energy that sweep across the cosmos like a lighthouse. From Earth, we see such a beam as on-and-off pulses — hence the name “pulsar.”
Some pulsars have companions — “normal” stars like the Sun, or perhaps the “failed” stars known as brown dwarfs. Radiation from the pulsar heats the companion, causing it to puff up and lose its grip on the hot gas at its surface. Some of the gas is pulled in by the pulsar, causing it to spin faster — up to hundreds of times per second.
But pulling material off the surface of its companion is only half of the story of a black widow.
In some cases, the pulsar’s radiation also erodes the surface of its companion like a blowtorch, with gas streaming away from the pulsar. Over time, the combination of accretion — pulling material into the pulsar — and erosion — blasting stuff away from the pulsar — can completely destroy the companion.
So far, astronomers have caught only a handful of black widows in the process of destroying their companions. But they suspect that many more have already finished the deed — dead stars that have devoured their mates.
Script by Damond Benningfield, Copyright 2014