No one ever accused Jupiter of modesty: The sun's largest planet boasts a diameter spanning 11.2 Earths. But earlier Jupiter-like planets may have put our own gas giant to shame. A new analysis of data from NASA's Kepler spacecraft finds that stars with lower abundances of heavy elements—the kind that populated the early Milky Way—are more likely to host gas giants several thousand kilometers larger in diameter than Jupiter. Although tentative, this correlation makes sense: the fewer metals a Jupiter-mass gas giant possesses, the more lightweight hydrogen and helium it has, so the bigger and fluffier the planet should be. The new work, to appear in The Astrophysical Journal, means that even though Jupiter is named after the king of the gods, it may have to bow to its planetary elders.
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