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Doomed Planets

June 12, 2015

Kepler-78b is doomed. The small planet orbits a star that’s about 400 light-years away in Cygnus, the swan. The constellation spreads its wings in the eastern sky after it gets good and dark right now, and soars high overhead later on.

Astronomers have confirmed almost 2,000 planets in other star systems. Most of these worlds probably will outlive their stars — but some won’t. They’ll fall into their parent star, be blasted apart by the star’s heat, or be ripped apart by its gravity.

Kepler-78b is a ball of rock that’s a bit bigger and heavier than Earth. But it’s only a million miles away from its star — about one percent of the distance from Earth to the Sun. Its surface is probably completely covered in molten rock. And the planet is inching closer to the star. In a few billion years, it’ll get so close that the star’s gravity will rip the planet apart.

Other planets won’t have to wait nearly so long. Two planets that orbit a star known as Kepler-56 will expire in the next 150 million years or so as their star expands and swallows them. And a planet in another star system will vanish at about the same time — blasted away by energy and particles from its nearby sun.

The planet with the shortest remaining known lifetime is Wasp-18b. The giant planet is just a couple of million miles from its star, and moving closer. Astronomers estimate that it’ll fall into its star in less than a million years — a cosmic blink of an eye.


Script by Damond Benningfield, Copyright 2015

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