Near Earth-Size Rocky Planets May Be Left Over Gas Giant Cores

NASA's Kepler Space Telescope has discovered two Earth-sized planets orbiting a very distant star. The two planets are 0.76 and 0.87 times the Earth's radius. The planets are thought to have once been much larger. The smaller rocky planets discovered are believed to be all that's left of once larger gas giant planets. The two planets are the smallest ever discovered orbiting around an active star.

Astronomers studying the newly discovered planets think that they were once gas giants along the lines of Saturn or Jupiter. They became the small rocky planets that were discovered after the parent star became a red giant and burned off the outer gas layers. Any planets that orbited closer to the parent star would have been vaporized when the star expanded.

The two planets are orbiting a subdwarf parent star called KIC 02697388. The star is about 4,000 light-years away in the direction of the Cygnus constellation. A Subdwarf B star is a very hot blue star that is between a red giant and white dwarf star that is in the final stages of its life cycle.

[via National Geographic]