Planet Neptune
Neptune
Discovered by Johann Gotfried Galle
Date of discovery September 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 eccentricity 0.0097
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 albedo 0.41
Magnitude (Vo) 7.84
Mean cloud temperature -193 to -153C
Atmospheric pressure (bars) 1-3
Atmospheric composition: Hydrogen 85%, Helium 13%, Methane 2%