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Picture taken during Apopllo 11 mission, 16 July 1969. Credit: NASA Origin of name
The name Earth comes from the Indo-European base 'er' from which similar names are derived in other European languages.

ESA Missions
ESA's Earth Observation programme comprises several dedicated satellites:
Envisat,  ERS 1&2,  MetOp,  MSG-1,  Proba and  Earth Explorers.

Earth Observation programme
Images of our planet from orbit are acquired continuously by several dedicated satellites. They have become powerful scientific tools to enable better understanding and improved management of the Earth and its environment.



Physical Properties


Property Unit Value
Equatorial radius km 6378.1
Polar radius km 6356.8
Core radius km 3485
Flattening   0.00335
Mass  (x1024) kg 5.9736
Volume  (x1010) km3 108.321
Mean density kgm-3 5515
Surface gravity at equator ms-2 9.798
Escape velocity kms-1 11.186
Magnetic field at equator  (x10-4) T 0.305
Magnetic dipole moment  (x1015) Tm3 7.91
Tilt of dipole axis ° 11.7
Dipole field centre offset from planet centre (equatorial radii)   0.07
Number of natural satellites   1


Orbital Parameters


Parameter Unit Value
Perihelion  (x106) km 147.09
Aphelion  (x106) km 152.10
Mean distance from the Sun  (x106) km 149.60
Mean distance from the Sun AU 1.00
Eccentricity   0.0167
Sidereal orbit period d 365.256
Sidereal rotation period h 23.935
Length of day h 24.000
Orbit inclination to Eliptic ° 0.000
Mean orbital velocity kms-1 29.78
Maximum orbital velocity kms-1 30.29
Minimum orbital velocity kms-1 29.29
Axial tilt ° 23.45


  • 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
5-Oct-2023 03:31 UT

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