Two Earth-Size Planets Born of Battered "Jupiter"?
Worlds orbiting a dying star may be pieces of a broken gas giant, study hints.
The planetary pair—discovered using NASA's Kepler space telescope and announced in the journal Nature last December—are just under Earth's radius. Both orbit a so-called subdwarf B star dubbed KIC 05807616, which sits about 4,000 light-years away.
(Also see "Smallest Exoplanets Found—Each Tinier Than Earth.")
When sunlike stars run out of hydrogen fuel, they enter a red giant phase, in which their gas envelopes can swell to several hundred times their original size.
Eventually a red giant's gas envelope will slough off entirely, leaving behind a dense stellar corpse known as a white dwarf. Sometimes, however, a red giant will lose its gas envelope prematurely to form a subdwarf B star, like KIC 05807616.
The scientists who discovered the roughly Earth-size planets
