mirrored file at http://SaturnianCosmology.Org/ For complete access to all the files of this collection see http://SaturnianCosmology.org/search.php ========================================================== ___________________________________ Neptune Fact Sheet ___________________________________ [1][Image of Neptune] _________________________________________________________________ Neptune/Earth Comparison _________________________________________________________________ Bulk parameters Neptune Earth Ratio (Neptune/Earth) Mass (10^24 kg) 102.43 5.9736 17.147 Volume (10^10 km^3) 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/m^3) 1,638 5,515 0.297 Gravity (eq., 1 bar) (m/s^2) 11.15 9.80 1.14 Acceleration (eq., 1 bar) (m/s^2) 11.00 9.78 1.12 Escape velocity (km/s) 23.5 11.19 2.10 GM (x 10^6 km^3/s^2) 6.8351 0.3986 17.15 Bond albedo 0.290 0.306 0.95 Visual geometric albedo 0.41 0.367 1.12 Visual magnitude V(1,0) -6.87 -3.86 - Solar irradiance (W/m^2) 1.51 1,367.6 0.0011 Black-body temperature (K) 46.6 254.3 0.183 J[2] (x 10^-6) 3411. 1082.63 3.151 Number of natural satellites 13 1 Planetary ring system Yes No _________________________________________________________________ Orbital parameters Neptune Earth Ratio (Neptune/Earth) Semimajor axis (10^6 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 (10^6 km) 4,444.45 147.09 30.216 Aphelion (10^6 km) 4,545.67 152.10 29.886 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 Length of day (hrs) 16.11 24.0000 0.671 Obliquity to orbit (deg) 28.32 23.45 1.208 * Magnetic coordinates (as determined by the Voyager 2 Radio Science experiment) _________________________________________________________________ Neptune Observational Parameters Discoverer: Johann Gottfried Galle (based on predictions by John Couch Adams and Urbain Leverrier) Discovery Date: 23 September 1846 Distance from Earth Minimum (10^6 km) 4305.9 Maximum (10^6 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 (10^6 km) 4347.31 Apparent diameter (seconds of arc) 2.3 Apparent visual magnitude 7.8 Maximum apparent visual magnitude 7.78 Neptune Mean Orbital Elements (J2000) 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 _________________________________________________________________ North Pole of Rotation 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 = 359.28 + 549.308T degrees T = Julian centuries from reference date _________________________________________________________________ Neptunian Magnetosphere Goddard Space Flight Center OTD (O8) Model Dipole field strength: 0.142 gauss-Rn^3 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 _________________________________________________________________ Neptunian Atmosphere 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/m^3 Wind speeds: 0-200 m/s Scale height: 19.1 - 20.3 km Mean molecular weight: 2.53 - 2.69 g/mole Atmospheric composition (by volume, uncertainty in parentheses) Major: Molecular hydrogen (H[2]) - 80.0% (3.2%); Helium (He) - 19.0% (3.2%); Methane (CH[4]) 1.5% (0.5%) Minor (ppm): Hydrogen Deuteride (HD) - 192; Ethane (C[2]H[6]) - 1.5 Aerosols: Ammonia ice, water ice, ammonia hydrosulfide, methane ice(?) _________________________________________________________________ If no sub- or superscripts appear on this page - for example, if the "Mass" is given in units of "(1024 kg)" - you may want to check the [2]notes on the sub- and superscripts. [3]bullet Notes on the factsheets - definitions of parameters, units, notes on sub- and superscripts, etc. _________________________________________________________________ [4]bullet Neptunian Satellite Fact Sheet [5]bullet Neptunian Rings Fact Sheet [6]bullet Planetary Fact Table - metric units [7]bullet Planetary Fact Table - U.S. units [8]bullet Planetary Fact Table - Earth ratio [9]bullet Neptune Home Page [10]bullet Directory to other Planetary Fact Sheets [11]bullet NSSDC Planetary Home Page _________________________________________________________________ Questions and comments about this page should be addressed to: Dr. David R. Williams, [12]dwilliam at nssdc.gsfc.nasa.gov, +1-301-286-1258 NSSDC, Mail Code 633, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 or Dr. Edwin V. Bell II, [13]ed.bell at gsfc.nasa.gov, +1-301-286-1187 NSSDC, Mail Code 633, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 [NSSDC logo] _________________________________________________________________ NASA Official: Ed Grayzeck, edwin.j.grayzeck at nasa.gov Last Updated: 09 November 2003, DRW References 1. http://nssdc.gsfc.nasa.gov/planetary/image/neptune_voy2.jpg 2. http://nssdc.gsfc.nasa.gov/planetary/factsheet/fact_notes.html 3. http://nssdc.gsfc.nasa.gov/planetary/factsheet/fact_notes.html 4. http://nssdc.gsfc.nasa.gov/planetary/factsheet/neptuniansatfact.html 5. http://nssdc.gsfc.nasa.gov/planetary/factsheet/nepringfact.html 6. http://nssdc.gsfc.nasa.gov/planetary/factsheet/index.html 7. http://nssdc.gsfc.nasa.gov/planetary/factsheet/planet_table_british.html 8. http://nssdc.gsfc.nasa.gov/planetary/factsheet/planet_table_ratio.html 9. http://nssdc.gsfc.nasa.gov/planetary/planets/neptunepage.html 10. http://nssdc.gsfc.nasa.gov/planetary/planetfact.html 11. http://nssdc.gsfc.nasa.gov/planetary/planetary_home.html 12. mailto:dwilliam at nssdc.gsfc.nasa.gov 13. mailto:ed.bell at gsfc.nasa.gov