| Neptune |
Earth |
Ratio (Neptune/Earth) |
|
|---|---|---|---|
| Mass (1024 kg) | 102.409 | 5.9722 | 17.15 |
| Volume (1010 km3) | 6,254 | 108.321 | 57.74 |
| Equatorial radius (1 bar level) (km) | 24,764 | 6,378.1 | 3.883 |
| Polar radius (1 bar level) (km) | 24,341 | 6,356.8 | 3.829 |
| Volumetric mean radius (km) | 24,622 | 6,371.0 | 3.865 |
| Ellipticity (Flattening) | 0.01708 | 0.00335 | 5.10 |
| Mean density (kg/m3) | 1,638 | 5,513 | 0.297 |
| Gravity (mean, 1 bar) (m/s2) | 11.27 | 9.82 | 1.15 |
| Acceleration (eq., 1 bar) (m/s2) | 11.00 | 9.78 | 1.12 |
| Acceleration (pole, 1 bar) (m/s2) | 11.41 | 9.83 | 1.16 |
| Escape velocity (km/s) | 23.5 | 11.19 | 2.10 |
| GM (x 106 km3/s2) | 6.8351 | 0.39860 | 17.15 |
| Bond albedo | 0.290 | 0.294 | 0.99 |
| Geometric albedo | 0.442 | 0.434 | 1.02 |
| V-band magnitude V(1,0) | -6.94 | -3.99 | - |
| Solar irradiance (W/m2) | 1.508 | 1,361.0 | 0.0011 |
| Black-body temperature (K) | 46.6 | 254.3 | 0.183 |
| J2 (x 10-6) | 3411. | 1082.63 | 3.151 |
| Number of natural satellites | 16 | 1 | |
| Planetary ring system | Yes | No |
| Neptune |
Earth |
Ratio (Neptune/Earth) |
|
|---|---|---|---|
| Semimajor axis (106 km) | 4,514.953 | 149.598 | 30.178 |
| Sidereal orbit period (days) | 60,189.018 | 365.256 | 164.79 |
| Tropical orbit period (days) | 59,799.900 | 365.242 | 163.73 |
| Perihelion (106 km) | 4,471.050 | 147.095 | 30.396 |
| Aphelion (106 km) | 4,558.857 | 152.100 | 29.973 |
| Synodic period (days) | 367.49 | - | - |
| Mean orbital velocity (km/s) | 5.45 | 29.78 | 0.183 |
| Max. orbital velocity (km/s) | 5.47 | 30.29 | 0.181 |
| Min. orbital velocity (km/s) | 5.37 | 29.29 | 0.183 |
| Orbit inclination (deg) | 1.770 | 0.000 | - |
| Orbit eccentricity | 0.0097 | 0.0167 | 0.581 |
| Sidereal rotation period (hrs) | 16.11* | 23.9345 | 0.673 |
| Length of day (hrs) | 16.11 | 24.0000 | 0.671 |
| Obliquity to orbit (deg) | 28.32 | 23.44 | 1.208 |
| Inclination of equator (deg) | 28.32 | 23.44 | 1.208 |
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) 4319.0
Maximum (106 km) 4711.0
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) 4348.66
Apparent diameter (seconds of arc) 2.3
Apparent visual magnitude 7.7
Maximum apparent visual magnitude 7.67
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
Right Ascension: 299.36 + 0.70 sin N Declination : 43.46 - 0.51 cos N Reference Date : 12:00 UT 1 Jan 2000 (JD 2451545.0) N = 357.85 + 52.316T degrees T = Julian centuries from reference date
Dipole field strength: 0.142 Gauss-Rn3
Dipole tilt to rotational axis: 46.9 degrees
Longitude of tilt: 288 degrees (IAU convention)
Dipole offset: 0.485 Rn
Surface (1 Rn) field strength: ~0.1 - 0.9 Gauss
Rn denotes Neptunian model radius, here defined to be 24,765 km
Surface Pressure: >>1000 bars Temperature at 1 bar: 72 K (-201 C) Temperature at 0.1 bar: 55 K (-218 C) Density at 1 bar: 0.45 kg/m3 Wind speeds: 0-580 m/s Scale height: 19.1 - 20.3 km Mean molecular weight: 2.53 - 2.69 Atmospheric composition (by volume, 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(?)
Notes on the factsheets
- definitions of parameters, units, notes on sub- and superscripts, etc.
Neptunian Satellite Fact Sheet
Neptunian Rings Fact Sheet
Planetary Fact Table
- metric units
Planetary Fact Table
- U.S. units
Planetary Fact Table
- Earth ratio
Neptune Home Page
Directory to other Planetary Fact Sheets
Author/Curator: