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Solar System Exploration
Proteus: Facts & Figures
   Back to Neptune   Overview   Gallery   Facts & Figures   News 
Discovered By
S. Synnott, Voyager 2
Date of Discovery
Orbit Size Around Neptune (semi-major axis)
Metric: 117,646 km
English: 73,102 miles
Periapsis (closest)
Metric: 117,587 km
Apoapsis (farthest)
Metric: 117,705 km
Sidereal Orbit Period (Length of Year)
0.003071869 Earth years
1.122 Earth days
Orbit Circumference
Metric: 739,191.57 km
Average Orbit Velocity
Metric: 27,450.7 km/h
Orbit Eccentricity
Orbit Inclination
0.075 degree
Mean Radius
Metric: 210.0 km
By Comparison: 218 x 208 x 201 km, tri-axial
Equatorial Circumference
Metric: 1,319.5 km
Metric: 38,792,386 km3
Metric: 50,355,259,352,065,700,000 kg
Scientific Notation: 5.0355 x 1019 kg
Metric: 1.3 g/cm3
Surface Area
Metric: 554,176.94 km2
Surface Gravity
Metric: 0.76 m/s2
Escape Velocity
Metric: 644 km/h
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Last Updated: 12 Aug 2013