Pluto is now considered a Dwarf planet, demoted in 2006 in by the IUA. A planet is “a celestial body that
- (a) is in orbit around the Sun,
- (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape,
- (c) has cleared the neighborhood around its orbit.”
Pluto is named after the Greek god of the underworld.
Pluto was reclassified from a planet to a dwarf planet in 2006:
Pluto was discovered on February 18th, 1930 by the Lowell Observatory:
Pluto has five known moons:
Pluto may be the largest dwarf planet. (Or it could be Eris)
Pluto is smaller than a number of moons including the Earth's moon. Pluto has 66% of the diameter of the Earth’s moon and 18% of its mass.
Pluto has a eccentric and inclined orbit:
This takes it between 4.4 and 7.4 billion km from the Sun meaning Pluto is periodically closer to the Sun than Neptune.
No spacecraft have visited Pluto:
Though in July 2015 the spacecraft New Horizons, which was launched in 2006, is scheduled to fly by Pluto on its way to the Kuiper Belt.
Pluto sometimes has an atmosphere:
During Pluto’s elliptical when Pluto is closer to the Sun its surface ice thaws and forms a thin atmosphere primarily of nitrogen with a little methane and carbon monoxide. When Pluto travels away from the Sun the atmosphere then freezes back to its solid state.
Orbit Period: 246.04 Earth years
Surface Temperature: -229°C