Neptune Statistics
 Discovered byJohann Gotfried Galle 
 Date of discoverySeptember 23, 1846 
 Mass (kg)1.024e+26 
 Mass (Earth = 1)1.7135e+01 
 Equatorial radius (km)24,746 
 Equatorial radius (Earth = 1)3.8799e+00 
 Mean density (gm/cm^3)1.64 
 Mean distance from the Sun (km)4,504,300,000 
 Mean distance from the Sun (Earth = 1)30.0611 
 Rotational period (hours)16.11 
 Orbital period (years)164.79 
 Mean orbital velocity (km/sec)5.45 
 Orbital eccentricity0.0097 
 Tilt of axis (degrees)28.31 
 Orbital inclination (degrees)1.774 
 Equatorial surface gravity (m/sec^2)11.0 
 Equatorial escape velocity (km/sec)23.50 
 Visual geometric albedo0.41 
 Magnitude (Vo)7.84 
 Mean cloud temperature-193 to -153°C 
 Atmospheric pressure (bars)1-3 
 Atmospheric composition
Hydrogen
Helium
Methane

85% 
13% 
2% 

Ring Statistics

NameDistance*WidthThicknessMassAlbedo
1989N3R41,900 km15 km??low
1989N2R53,200 km15 km??low
1989N4R53,200 km5,800 km??low
1989N1R62,930 km< 50 km??low

*The distance is measured from the planet center to the start of the ring.

Moon Statistics
Moon#Radius
(km)		Mass
(kg)		Distance
(km)		DiscovererDate
NaiadIII29?48,000Voyager 21989
ThalassaIV40?50,000Voyager 21989
DespinaV74?52,500Voyager 21989
GalateaVI79?62,000Voyager 21989
LarissaVII104x89?73,600Voyager 21989
ProteusVIII200?117,600Voyager 21989
TritonI1,3502.14e+22354,800W. Lassell1846
NereidII170?5,513,400G. Kuiper1949

Neptune Data Aquired From Views of the Solar System
by Calvin J. Hamilton

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