Sponsored by the Institute of Physics   Planets   Mercury   Venus   Earth   Mars   Jupiter   Saturn   Uranus   Neptune     Rings     Naiad     Thalassa     Despina     Galatea     Larissa     Proteus     Triton     Nereid   Pluto Asteroids Comets Constellations Sunrise and Sunset Times Moon Phases SI Units Symbols   Printer Version Astronomy Planets - Neptune Bulk Parameters | Orbital Parameters Observational Parameters | Atmospheric Parameters Satellites Bulk Parameters Mass 102.43 × 1024 kg Volume 6 254 × 1010 km3 Equatorial Radius (Defined by Pressure = 1 bar) 24 766 km Polar Radius (Defined by Pressure = 1 bar) 24 342 km Volumetric Mean Radius 24 624 km Ellipticity 0.017 1 Mean Density 1 638 kg m-3 Surface Gravity (At Pressure = 1 bar) 11.00 m s-2 Escape Velocity 23.5 km s-1 GM 6.8351 × 106 km3 s-2 Bond Albedo 0.82 Visual Geometric Albedo 0.41 Visual Magnitude -6.87 Solar Irradiance 1.47 W m-2 Black-Body Temperature 33.2 K Orbital Parameters Semimajor Axis 4 498.3 × 106 km Sidereal Orbit Period 60 189.0 days Tropical Orbit Period 59 799.9 days Perihelion 4 458.0 × 106 km Aphelion 4 535.2 × 106 km Synodic Period 367.49 days Mean Orbital Velocity 5.48 km s-1 Orbital Inclination 1.769 ° Orbital Eccentricity 0.008 59 Sidereal Rotation Period (Magnetic Coordinates, determined by Voyager 2 Radio Science Experiment) 16.11 hours Obliquity to Orbit 29.56 ° Observational Parameters Maximum Apparent Diameter from Earth 2.4 arc seconds Minimum Apparent Diameter from Earth 2.2 arc seconds Maximum Distance from Earth 4 687.3 × 106 km Minimum Distance from Earth 4 305.9 × 106 km Apparent Magnitude near Opposition 7.8 Atmospheric Parameters Surface Pressure Much more than 100 bars Average Temperature about 58 K Temperature at 1 bar about 72 K Density at 1 bar about 0.45 kg m-3 Scale Height 19.1 km to 20.3 km Wind Speeds 0 to 200 m s-1 Mean Molecular Weight 2.53 g mol-1 to 2.69 g mol-1 Molecular Hydrogen H2 80% Helium He 19% Methane CH4 1.5% Hydrogen Deuteride HD 105 ppm Ethane C2H6 1.5 ppm Ammonia Ice Water Ice Ammonia Hydrosulphide Methane Ice Satellites Naiad Larissa Thalassa Proteus Despina Triton Galatea Nereid   [ H O M E ] [ S C I E N C E ] [ M A T H S ] [ A S T R O N O M Y ] Download | Shop | Contact | About   Page compiled: Wed Sep 05 18:38:01 GMT+01:00 2001