The iron planet with a 4-hour year

 作者:南郭仵     |      日期:2019-03-07 03:20:01
AN IRON planet orbiting a sun-like star has the shortest known year: 4 hours, 15 minutes. Found by NASA’s Kepler space telescope, KOI 1843.03 is so close to its star that one side is probably locked facing the star and feels more of its gravitational pull. This would create tidal forces that squash and stretch the planet. To withstand the star’s wrath, the planet must be at least 70 per cent iron, says Roberto Sanchis-Ojeda, a graduate student at the Massachusetts Institute of Technology (Astrophysical Journal Letters, doi.org/njr). It’s a puzzle how such closely orbiting planets form, says Dimitar Sasselov of Harvard University,