This is the Web Edition of "A Trip Into Space", a Coimbra-based electronic book on space science. Both the texts and the photos are by courtesy of National Aeronautics and Space Administration.
| This is the Web Edition of "A Trip Into Space", a Coimbra-based electronic book on space science. Both the texts and the photos are by courtesy of National Aeronautics and Space Administration.
|
A Trip Into Space  Fact Sheets Neptune Fact Sheet |
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| See also: Notes On The Fact Sheets |   |
Neptune Earth Ratio (Neptune/Earth)
Mass (1024 kg) 102.43 5.9736 17.147
Volume (1010 km3) 6,254 108.321 57.74
Radius (1 bar level) (km)
Equatorial 24,764 6,378.1 3.883
Polar 24,341 6,356.8 3.829
Volumetric mean radius (km) 24,624 6,371.0 3.865
Ellipticity (Flattening) 0.01708 0.00335 5.10
Mean density (kg/m3) 1,638 5,515 0.297
Gravity (eq., 1 bar) (m/s2) 11.00 9.78 1.12
Escape velocity (km/s) 23.5 11.19 2.10
GM (x 106 km3/s2) 6.8351 0.3986 17.15
Bond albedo 0.82 0.385 2.13
Visual geometric albedo 0.41 0.367 1.12
Visual magnitude V(1,0) -6.87 -3.86 -
Solar irradiance (W/m2) 1.51 1,367.6 0.0011
Black-body temperature (K) 33.2 247.3 0.134
J2 (x 10-6) 3411. 1082.63 3.151
Neptune Earth Ratio (Neptune/Earth)
Semimajor axis (106 km) 4,495.06 149.60 30.047
Sidereal orbit period (days) 60,189. 365.256 164.79
Tropical orbit period (days) 59,799.9 365.242 163.73
Perihelion (106 km) 4,545.67 147.09 30.904
Aphelion (106 km) 4,444.45 152.10 29.221
Synodic period (days) 367.49 - -
Mean orbital velocity (km/s) 5.43 29.78 0.182
Max. orbital velocity (km/s) 5.50 30.29 0.182
Min. orbital velocity (km/s) 5.37 29.29 0.183
Orbit inclination (deg) 1.769 0.000 -
Orbit eccentricity 0.0113 0.0167 0.677
Sidereal rotation period (hours) 16.11* 23.9345 0.673
Obliquity to orbit (deg) 28.32 23.45 1.208
* Magnetic coordinates (as determined by the Voyager 2 Radio Science experiment)
Discoverer: Johann Gottfried Galle (based on predictions by
John Couch Adams and Urbain Leverrier)
Discovery Date: 23 September 1846
Distance from Earth
Minimum (106 km) 4305.9
Maximum (106 km) 4687.3
Apparent diameter from Earth
Maximum (seconds of arc) 2.4
Minimum (seconds of arc) 2.2
Mean values at opposition from Earth
Distance from Earth (106 km) 4347.31
Apparent diameter (seconds of arc) 2.3
Apparent visual magnitude 7.8
Semimajor axis (AU) 30.06896348 Orbital eccentricity 0.00858587 Orbital inclination (deg) 1.76917 Longitude of ascending node (deg) 131.72169 Longitude of perihelion (deg) 44.97135 Mean Longitude (deg) 304.88003
Dipole field strength: 0.142 gauss-Rn3
Dipole tilt to rotational axis: 46.9 degrees
Longitude of tilt: 288 degrees (IAU convention)
Dipole offset (planet center to dipole center) distance: 0.55 Rn
Note: Rn denotes Neptunian radii, here defined to be 24,765 km
Surface Pressure: >>100 bars
Average temperature: ~58 K
Temperature at 1 bar: ~72 K
Density at 1 bar: ~0.45 kg/m3
Wind speeds: 0-200 m/s
Scale height: 19.1 - 20.3 km
Mean molecular weight: 2.53 - 2.69 g/mole
Atmospheric composition (uncertainty in parentheses)
Major: Molecular hydrogen (H2) - 80.0% (3.2%); Helium (He) - 19.0% (3.2%);
Methane (CH4) 1.5% (0.5%)
Minor (ppm): Hydrogen Deuteride (HD) - ~192; Ethane (C2H6) - ~1.5
Aerosols: Ammonia ice, water ice, ammonia hydrosulfide, methane ice(?)
Last Update: 2004-Nov-27