At half Neptune’s size, exoplanet should be gassy — but it’s not
When it comes to big balls of rock, exoplanet BD+20594b might have all other known worlds beat. At roughly half the diameter of Neptune, BD+20594b is 100 percent rock, researchers suggest online January 28 at arXiv.org. The planet seems to defy recent calculations that indicate a planet this large should be gassy (SN: 8/22/15, p. 32).
BD+20594b sits about 500 light-years away in the constellation Taurus. The planet is about 16 times as massive as Earth but just a little over twice as wide, making its density about 8 grams per cubic centimeter, Néstor Espinoza, an astrophysicist at the Pontifical Catholic University of Chile in Santiago, and colleagues report. Earth’s density, by comparison, is 5.5 grams