New “Deep Fried” Planets Found—Survivors of Star Death
Imaged Above: An artist’s impression of planets orbiting close to a hot sub dwarf star. Illustration courtesy S. Charpinet
Two newfound Earth-size planets are probably the charred survivors of a near-death encounter with their fading parent star, scientists say.
The planetary pair, discovered using NASA’s Kepler space telescope, are about 0.76 and 0.87 times Earth’s radius, making the alien worlds the smallest planets detected so far around an active star, other than our sun.
But the planets didn’t start small—astronomers think the worlds were once gas giants, akin to Jupiter or Saturn, that were stripped down after being swallowed by their swollen, aging parent.
News of the “deep fried” duo comes hot on the heels of the announcement of the first Earth-size planets found by the Kepler team.
Just yesterday scientists announced the discovery of Kepler-20e and Kepler-20f, two planets that are 0.87 and 1.03 times Earth’s radius, respectively.
There are some similarities between the Earth-size planets discovered so far, said Valérie Van Grootel, an astronomer at the University of Liège in Belgium and a co-author on the latest study.
Kepler-20e and -20f “orbit very close to their star, so they are very hot planets, and that is the case with our planets, too,” Van Grootel told National Geographic News.
“But there are major differences, too. In our case, we have a post red-giant star, whereas the other team’s planets orbit a star like our own sun. We think that our Earth-size planets are the rocky cores of former gas planets.”
Meanwhile, interactions with gases in a red giant star’s expanded atmosphere will force some planets a bit farther from the star to migrate inward—which actually gives those worlds a shot at survival.
Scientists think the newly discovered Earth-size planets were once gas giants that got sucked in toward the star during its red giant phase.
As the planets plowed through their star’s hot atmosphere, their gaseous and liquid layers were stripped off, leaving behind only the rocky cores.