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Image credit: Alan Stern (Southwest Research Institute), Marc Buie (Lowell Observatory), NASA and ESA Origin of name
Pluto is named after the Greek god of the underworld.

Discovered by
Clyde Tombaugh in 1930

Naming convention
Surface features on Pluto are named after deities of the underworld.

Once considered to be the ninth planet in the Solar System, Pluto was reclassified as a dwarf planet in 2006.


Physical Properties


Property Unit Value Earth = 1
Equatorial radius km 1195 0.187
Polar radius km 1195 0.180
Flattening   0.0000 0.0
Mass  (x1024) kg 0.0125 0.0021
Volume  (x1010) km3 0.715 0.0066
Mean density kgm-3 1750 0.317
Surface gravity at equator ms-2 0.58 0.059
Escape velocity kms-1 1.2 0.107
Number of natural satellites   3  


Orbital Parameters


Property Unit Value
Perihelion  (x106) km 4434.99
Aphelion  (x106) km 7304.33
Mean distance from the Sun  (x106) km 5900.1
Mean distance from the Sun AU 39.44
Eccentricity   0.2444
Sidereal orbit period y 247.68
Sidereal rotation period h R 153.293
Length of day h 153.282
Orbit inclination to Ecliptic ° 17.16
Mean orbital velocity kms-1 4.72
Maximum orbital velocity kms-1 6.10
Minimum orbital velocity kms-1 3.71
Axial tilt ° 122.53



  • Sidereal orbit period
    The time taken by the planet to complete exactly one orbit around the Sun with respect to the celestial sphere.
  • Sidereal rotation period
    The time in which the planet rotates around its axis exactly 360° with respect to the celestial sphere.
  • Length of a day
    Defined as the time between two successive sunrises over the meridian.
  • Magnetic dipole moment
    Calculated as the ratio of the magnetic field strength at the equator divided by the cube of the equatorial radius.


Last Update: 1 September 2019
18-May-2021 23:21 UT

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