A stellar corpse in the constellation Scorpius isn’t a good neighbor. It’s blasting a small companion star with a particle beam. That causes the companion to flare up every couple of minutes.

AR Scorpii stands close to Antares, the scorpion’s bright orange heart, which is not far to the lower right of the Moon at nightfall. AR Scorpii is quite faint, though, so it takes a big telescope to spot it.

The system consists of two stars. One of them is a white dwarf — the hot, dense “corpse” of a once-normal star. The other is a red dwarf — a small, cool star that’s still in the prime of life. The two are separated by about half a million miles, which is only twice the distance between Earth and the Moon.

The white dwarf spins once every couple of hours — a fast rate for a white dwarf. It might have spun up by “stealing” gas from its companion. As the gas poured onto the white dwarf, it sped up the star’s rotation like a parent pushing a child on a merry-go-round.

That high-speed ride helps the white dwarf generate a powerful magnetic field, which accelerates charged particles near the white dwarf to almost the speed of light. As the white dwarf rotates, that creates twin beams, like those from a lighthouse.

The beams sweep across the companion star every couple of minutes. That zaps the surface of the star, making it much hotter for a few seconds. So AR Scorpii grows noticeably brighter every two minutes — as a dead star zaps its close companion.


Script by Damond Benningfield

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