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Voyager 2 image. Copyright: Calvin J. Hamilton Origin of name
Uranus is named after the father of Saturn in Roman mythology.

Discovered by
William Herschel in 1781

Named after characters from Shakespeare's plays and from Pope's "Rape of the Lock".



Physical Properties


Property Unit Value Earth = 1
Equatorial radius, 1 bar level km 25 559 4.007
Polar radius, 1 bar level km 24 973 3.929
Flattening   0.02293 6.84
Mass  (x1024) kg 86.832 14.536
Volume  (x1010) km3 6833 63.08
Mean density kgm-3 1270 0.230
Gravity at equator, 1 bar level ms-2 8.87 0.905
Escape velocity kms-1 21.3 1.903
Magnetic field at equator  (x10-4) T 0.23 0.75
Magnetic dipole moment  (x1017) Tm3

~ 3.9

~ 50
Tilt of dipole axis ° 58.6  
Dipole field centre offset from planet centre (equatorial radii)   0.3  
Number of natural satellites   27  


Orbital Parameters


Property Unit Value
Perihelion  (x106) km 2741.30
Aphelion  (x106) km 3003.62
Mean distance from the Sun  (x106) km 2869.6
Mean distance from the Sun AU 19.182
Eccentricity   0.0457
Sidereal orbit period y 84.01
Sidereal rotation period
Magnetic coordinates (Voyager 2)
h R  17.24
Length of day h 17.24
Orbit inclination to Ecliptic ° 0.77
Mean orbital velocity kms-1 6.81
Maximum orbital velocity kms-1 7.11
Minimum orbital velocity kms-1 6.49
Axial tilt ° 97.77


  • 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
30-Sep-2020 03:15 UT

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