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Solar System Exploration
Themisto: Facts & Figures
   Back to Jupiter   Overview   Facts & Figures 
Discovered By
First time: Charles Thomas Kowal and Elizabeth Roemer
Second time: Scott Sander Sheppard, David C. Jewitt, Yanga Roland Fernández and Eugene A. Magnier
Date of Discovery
First time: 30 September 1975
Second time: 6 August 2000
Orbit Size Around Jupiter (semi-major axis)
Metric: 7,507,000 km
English: 4,664,634 miles
Periapsis (closest)
Metric: 5,687,303 km
Apoapsis (farthest)
Metric: 9,326,697 km
Sidereal Orbit Period (Length of Year)
0.355975359 Earth years
130.02 Earth days
Orbit Circumference
Metric: 46,467,175.95 km
Average Orbit Velocity
Metric: 14,891.0 km/h
Orbit Eccentricity
Orbit Inclination
Mean Radius
Metric: 4.0 (assuming an albedo of 0.04) km
English: 2.5 miles
Equatorial Circumference
Metric: 25.1 km
Metric: 268 km3
Metric: 689,387,479,224,709 kg
Scientific Notation: 6.8939 x 1014 kg
Metric: 2.6 g/cm3
Surface Area
Metric: 201.06 km2
Surface Gravity
Metric: 0.003 m/s2
Escape Velocity
Metric: 17 km/h

Additional Information:

USGS Astrogeology: Gazetteer of Planetary Nomenclature:

JPL Solar System Dynamics:

Solar System Moons: Discovery and Mythology by Jürgen Blunck; Springer-Verlag Berlin Heidelberg 2010

Encyclopedia of the Solar System, second edition; edited by Lucy-Ann McFadden, Paul R. Weissman, and Torrence V. Johnson; Academic Press 2007

Dr. Ellis Miner, retired planetary scientist, Jet Propulsion Laboratory
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Last Updated: 8 Mar 2011