NASA's Spots "Death Star" Cannibalizing Planet
In this artist’s conception, a tiny rocky object vaporizes as it orbits a white dwarf star.
Image by Mark Garlick
They called Star Wars science fiction, but it turns out there's a real live "death star" working its mojo in the Virgo constellation.
Astronomers announced Wednesday that they've discovered a rocky object spinning apart in a death spiral around a white dwarf star. This discovery could back up a long-held theory that white dwarfs are capable of cannibalizing remnant planets that have survived within their solar systems, according to a NASA release.
The scientists used the Kepler space telescope, used by NASA to hunt Earth-esque planets in the Milky Way Galaxy, to make the discovery, and then did a ton of ground observations to make sure they were actually right.
"We are for the first time witnessing a miniature 'planet' ripped apart by intense gravity, being vaporized by starlight and raining rocky material onto its star,” Andrew Vanderburg, a Harvard student and lead author of the paper on the discovery, published in Nature, says.
When observing the constellation Virgo astronomers noticed that the tiny planet orbiting the white dwarf had a tail on it, made by a dusty plume of debris and what they concluded was the signature of a small planet being vaporized.
Sun-like stars are fueled by nuclear reactions that turn hydrogen into helium but once all of that runs out the star burns the heavier stuff, expands to become very big very fast and then leaves an Earth-sized white dwarf star behind.
The "death star" white dwarf is being orbited by the vestiges of a planet, now believed to be about the size of a large asteroid. It's orbiting about 520,000 miles from the white dwarf, making the full circuit around the star every 4.5 hours. This orbital period places it extremely close to the white dwarf and its searing heat and shearing gravitational force which in turn tears it to pieces.
“The eureka moment of discovery came on the last night of observation with a sudden realization of what was going around the white dwarf,” Vanderburg says.
Once they realized the white dwarf was actually gobbling the remains of the planet, they went to work figuring out how the two got locked in this star-crossed celestial tango. They concluded that the planet was once a whole planet and its orbit became unstable and got kicked in toward the star. And then once it was stuck in the white dwarf's orbit it started coming apart.
So yeah, it's no moon. It's, well, a real live death star. Fingers crossed they name it Alderaan.
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