Astrophysics (index)about


(134340 Pluto)
(dwarf planet formerly listed as one of the nine planets)

Pluto (134340 Pluto) is a Dwarf Planet in an eccentric orbit ranging roughly from 30 AU (Neptune's distance) to 50 AU. It has a steeper Orbital Inclination than the eight planets: 17° from the Ecliptic. It and Neptune share an Orbital Resonance, with a ratio of 3:2.

Pluto was discovered in 1930 and was considered the ninth planet until the discovery of similar objects. Five Moon's are known:

  • Charon (discovered in 1978)
  • Nix (2005)
  • Hydra (2005)
  • Kerberos (2011)
  • Styx (2012)

Charon's mass is 1/6 of Pluto's and its radius about 1/2 Pluto's, by far the largest moon in the solar system compared its host planet/dwarf planet. In comparison, the Moon has 1/81 the mass and 1/4 the radius of Earth, and the Moon/Earth has been referred to as a Double Planet, since the size ratios of the other known moons to their host planets (Mars, Jupiter, etc.) are far greater.

The New Horizons mission observed Pluto during a 2015 flyby.

(minor planet)
/Lookback Years

Referenced by:
Current Sheet
Dwarf Planet
Embryo Barrier
Equilibrium Temperature (Teq)
Ethylene (C2H4)
International Astronomical Union (IAU)
Kuiper Airborne Observatory (KAO)
Kuiper Belt (K Belt)
Late Heavy Bombardment (LHB)
Lyapunov Time
Magnetic Field
New Horizons (NF1)
Ammonia (NH3)
Orbital Resonance
Planet Nine
Trans-Neptunian Object (TNO)