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Information about the planet Neptune
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Most frequently required information about Neptune
Neptune's Diameter: 49,528 km, 3.9 Earth Diameters
Planetary Mass: 1.02x1026 kg, 17.2 Earth masses
Average Distance from Sun: 4.497 billion km, 30.06 AU (astronomical units)
Length of Day: about 16 hours
Length of Year: 164.8 Earth Years
Number of natural satellites: 8
Planetary ring system: Yes
Average temperature: 59.3 degrees Kelvin
Atmospheric composition: Mosly Hydrogen (H2) - 80.0% and Helium (He) - 19.0%.
AU stands for astronomical unit.
One AU is the average distance from the center of the Earth to the center of the Sun: 149,597,870 km
Facts about Neptune's rings
Facts about Neptune's moons
Neptune
Mass (1024 kg) 102.43
Volume (1010 km3) 6,254
Radius (1 bar level) (km)
Equatorial 24,764
Polar 24,341
Ellipticity (Flattening) 0.01708 0.00335 5.10
Mean density (kg/m3) 1,638
Gravity (eq., 1 bar) (m/s2) 11.00
Escape velocity (km/s) 23.5
How many moons does Neptune have? 8 Facts about Neptune's moons
Planetary ring system Yes
Neptune Orbital parameters
Semimajor axis (106 km) 4,495.06
Sidereal orbit period (days) 60,189
Perihelion (106 km) 4,444.45
Aphelion (106 km) 4,545.67
Synodic period (days) 367.49
Orbit inclination (deg) 1.769
Orbit eccentricity 0.0113
Sidereal rotation period (hours) 16.11 Magnetic coordinates (as determined by the Voyager 2)
Length of day (hrs) 16.11
Obliquity to orbit (deg) 28.32
Neptune Observational ParametersDiscoverer: 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
Maximum apparent visual magnitude 7.78
Neptunian AtmosphereSurface 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: 0-200 m/s
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(?)
Information about Neptune supplied by the NASA Goddard Space Flight Center.
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