Pluto
/ˈpluːtəʊ/1
- Greek Mythology the god of the underworld【希腊神话】普路托, 冥王。亦称HADES.
2
- Astronomy the most remote known planet of the solar system, ninth in order from the sun, discovered in 1930 by Clyde Tombaugh【天文】冥王星。
Pluto usually orbits beyond Neptune at an average distance of 5, 900 million km from the sun, though its orbit is so eccentric that at perihelion it is closer to the sun than Neptune （as in 1979-99）. Pluto is smaller than earth's moon （diameter about 2, 250 km）, but it was discovered in 1978 to have its own satellite (Charon), which is so large that the pair should properly be regarded as a double planet.
词源
via Latin from Ploutōn, the Greek name of the god of the underworld.