Neptune

True-color Voyager 2 image.  August 20, 1989.


Orbital Elements
Mean distance from Sun4,504,300,000 km    =    30.0611 astronomical units
Perihelion distance4,444,450,000 km=    29.7093 astronomical units
Aphelion distance4,545,670,000 km=    30.3859 astronomical units
Eccentricity of orbit0.0097
Inclination of orbit1.774relative to Earth's orbit
Period of orbit164.79 years
Synodic period367 daysrelative to Earth
Mean orbital speed5.45 km/s
Minimum orbital speed5.37 km/s
Maximum orbital speed5.50 km/s
 
Physical Properties
Mean diameter49,248 km=    3.86  Earth diameters
Equatorial radius24,746 km
Oblateness1/40
Mass1.024 x 1026 kg=    17.135 Earth masses
Mean density1.64 g/cm3
Rotational period16.11 hours
Inclination of axis1.774relative to the axis of its orbit
Gravity at cloud tops11.0 m/s2
Escape speed23.5 km/sfrom cloud tops
Visual geometric albedo0.41
Visual magnitude (Vo)7.84maximum, as seen from Earth
Temperature of visible clouds    -193  to  -153C
Atmospheric pressure1 - 3 barsat cloud tops

Atmospheric Composition
Hydrogen85%
Helium13%
Methane  2%

Moons

One large moon and at least ten small moons.


HomeTo my Space and Science home page  for more about the Solar System

Jeff Root
September 4, 2003