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White Dwarfs IV

January 28, 2021

Not many planets are bigger than their stars. And not many have spiraled close to a dead star known as a white dwarf and survived. But astronomers recently discovered a planet that’s defied the odds in both of those cases.

WD 1856b orbits a white dwarf — the corpse of a star that was similar to the Sun. It’s about half as heavy as the Sun, but only about as big as Earth. It became a white dwarf at the end of its normal lifetime, almost six billion years ago.

1856b, on the other hand, is a giant planet. It’s about as big as Jupiter, the giant of our own solar system. That makes it several times wider than the white dwarf.

Astronomers discovered the planet with space telescopes, which saw the system’s light fade as the planet passed in front of the star. They confirmed it with telescopes on the ground, including the Hobby-Eberly Telescope at McDonald Observatory.

Astronomers have discovered the pulverized remains of planets orbiting white dwarfs. They’ve even seen the remains of dead planets polluting the surfaces of such stars. But this is the first time they’ve seen an intact planet this close to a white dwarf — just two million miles away.

The planet probably was born a lot farther out. As the star died, the planet’s orbit changed — it became extremely lopsided. Over time, the strong gravity of the white dwarf molded the orbit to its present configuration — just beyond the surface of a dead star.

Script by Damond Benningfield

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