60-Second Space

Ballooning Star Split Planet in Two

A recently discovered pair of exoplanets may be the wreckage of one formerly giant planet. John Matson reports

In about five billion years, Earth is going into the broiler. The sun will swell up into a red giant, engulfing us and the other inner planets. And that'll be that.

Or will it? Astronomers recently found two small planets orbiting very close to a star about 4,000 light-years away. The star has already passed through its red giant phase. So how did the planets survive? One idea was that the red giant had swallowed two formerly large planets and spit out the smaller cores. Imagine a star engulfing a Jupiter and leaving behind a scorched Earth—literally.

Now a new study proposes an even more violent explanation. Astrophysicists in Israel calculated that the two newfound planets might be the remnant of a single giant planet. That world would have been stripped to its core and then torn apart by the swelling star. The worlds now orbiting the former red giant would be the surviving, Earth-size chunks. ["A tidally destructed massive planet as the progenitor of the two light planets around the sdB star KIC 05807616," by Ealeal Bear and Noam Soker in The Astrophysical Journal Letters.]

So a planet much bigger than Earth can escape total destruction when its star goes red giant. Although being broiled, pulled apart like taffy and tossed away is no planetary picnic.

—John Matson

[The above text is a transcript of this podcast.]


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