Black Widows

Black Widows

Pulsars don’t play well with others. Some of them are destroying their companions, earning them an unflattering nickname: black widows.

Pulsars are the ultra-dense corpses of once-mighty stars. They’re up to a couple of times as massive as the Sun, but no bigger than a city. They’re called “pulsars” because they spin rapidly — up to hundreds of times per second — and we see “pulses” of energy with each spin.

Some pulsars have companions — stars or the stellar wannabes known as brown dwarfs. The pulsars bombard these unlucky mates with radiation and charged particles. That strips away material from the surface of the companion, creating a “wake” of hot gas behind it. Over time, that process may vaporize the companion. So like a female black widow spider, the pulsar destroys its mate.

The first black-widow pulsar was discovered in 1988. It’s about twice as massive as the Sun, and spins more than 600 times a second. Its companion is a brown dwarf — a “failed” star just two percent the Sun’s mass. They’re a little more than a million miles apart.

The brown dwarf eclipses the pulsar during each orbit. As the pulsar passes behind the brown dwarf’s wake, the charged particles amplify its pulses.

Eventually, though, the eclipses will end — as the pulsar whittles away its unlucky mate.

More about pulsars tomorrow.

Script by Damond Benningfield

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