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The Black Widow

The pulsar PSR B1957 +20 was the first millisecond pulsar to be discovered with a period of 640 revolutions per second. It reaches this speed because it steals mass and so devours its companion which was once a normal main sequence star.
The B star is hardly yet existent. We can only see the side of the sucked star that faces the pulsar. Once the pulsar has devoured its victim it will become slower.

Constellation: Sagittarius
Distance: 2500 light-years
Visual magnitude: 20
Orbit period of PSR B1957 +20 A and B: 9.2 hours

PSR B1957 +20 A

Diameter: circa 20 kilometers

PSR B1957 +20 B

Mass: 0.02 * Sun
Diameter: 1 * Sun

Back: List of Special Stars part 2
    The Black Widow
On the upper left is the cannibal pulsar, its victim is next to it. The stars' hot side is turned to us, otherwise we couldn't see it.
Photo: Nasa, Hubble Telescope

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