Pluto
Dwarf planet. Until its reclassification in 2006 it was considered to be the smallest and, usually, outermost planet of the Solar System. The existence of Pluto was predicted by calculation by US astronomer Percival Lowell and located by US astronomer Clyde Tombaugh in 1930. Its highly elliptical orbit occasionally takes it within the orbit of Neptune, as in 1979–99. Pluto has a mass about 0.002 of that of Earth.
Mean distance from the Sun
5.8 billion km/3.6 billion mi
Equatorial diameter
2,300 km/1,438 mi
Rotation period
6.39 Earth days
Year
248.5 Earth years
Atmosphere
thin atmosphere with small amounts of methane gas
Surface
low density, composed of rock and ice, primarily frozen methane; there is an ice cap at Pluto's north pole
Satellites
one moon, Charon
| Charon, Pluto's moon, was discovered 1978, revolving around Pluto with the same period as Pluto's rotation, remaining over the same point on Pluto's surface and showing the same face. It is composed mainly of ice and it is possible the pair may be a double planet system. Pluto has not yet been visited by a space probe, but the New Horizons probe, launched in 2006, is due to fly by Pluto in mid-2015. |
Pluto
In Greek mythology, lord of Hades, the underworld and also his original name. His Roman counterpart was Dis (also Orcus). He was the son of the Titans Kronos and Rhea; and brother of Zeus, Poseidon, Hera, Hestia, and Demeter. He abducted and married Persephone, daughter of the goddess of agriculture Demeter, causing winter on Earth; Persephone was eventually allotted six months of each year in Hades, and six with her mother.
| Pluto was swallowed at birth by Kronos who believed that his children would destroy him; Zeus, being hidden, later forced his father to regurgitate the siblings. In the ensuing battle, Pluto was given a helmet of darkness by the one-eyed giant Cyclops. Kronos was overthrown and his rule divided between the three gods: Zeus receiving the sky, Poseidon the sea, and Pluto the underworld. |
Worship The name Pluto, ‘giver of wealth’ (associated with minerals, crops, springs), was reputedly bestowed on the ruler of the underworld because no-one dared utter his original title Hades (initially Aides ‘unseen’). The name Hades was applied to his kingdom. Black sheep were sacrificed to him, the supplicant averting his eyes from the altar during the ritual. |
