出典:Wikipedia
出典:『Wikipedia』 (2011/03/30 00:31 UTC 版)
WASP-18b is an extrasolar planet that is notable for having an orbital period of less than one day. It has a mass equal to 10 Jupiter masses, just below the boundary line between planets and brown dwarfs, about 13 Jupiter masses. Due to tidal deceleration, it is expected to spiral towards and eventually merge with its host star, WASP-18, in less than a million years. The planet is approximately 3.1 million kilometres (1.9 million miles) from its star, which is about 325 light years from Earth. It was discovered by Coel Hellier, a professor of astrophysics at Keele University in England.