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Solar System Exploration
Neptune: Facts & Figures
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Discovered By
Urbain Le Verrier, John Couch Adams, Johann Galle
Date of Discovery
23 September 1846
Orbit Size Around Sun (semi-major axis)
Metric: 4,498,396,441 km
English: 2,795,173,960 miles
Scientific Notation: 4.4983964 x 109 km (3.0069923 x 101 A.U.)
By Comparison: 30.070 x Earth
Perihelion (closest)
Metric: 4,459,753,056 km
English: 2,771,162,074 miles
Scientific Notation: 4.45975 x 109 km (2.981 x 101 A.U.)
By Comparison: 30.318 x Earth
Aphelion (farthest)
Metric: 4,537,039,826 km
English: 2,819,185,846 miles
Scientific Notation: 4.53704 x 109 km (3.033 x 101 A.U.)
By Comparison: 29.830 x Earth
Sidereal Orbit Period (Length of Year)
164.79132 Earth years
60190.03 Earth days
By Comparison: 164.791 x Earth
Orbit Circumference
Metric: 28,263,736,967 km
English: 17,562,271,937 miles
Scientific Notation: 2.826 x 1010 km
By Comparison: 30.071 x Earth
Average Orbit Velocity
Metric: 19,566 km/h
English: 12,158 mph
Scientific Notation: 5.4349 x 103 m/s
By Comparison: 0.182 x Earth
Orbit Eccentricity
By Comparison: 0.514 x Earth
Orbit Inclination
1.77 degrees
Equatorial Inclination to Orbit
28.3 degrees
Mean Radius
Metric: 24,622 km
English: 15,299.4 miles
Scientific Notation: 2.4622 x 104 km
By Comparison: 3.8647 x Earth
Equatorial Circumference
Metric: 154,704.6 km
English: 96,129.0 miles
Scientific Notation: 1.54705 x 105 km
By Comparison: 3.8647 x Earth
Metric: 62,525,703,987,421 km3
English: 15,000,714,125,712 mi3
Scientific Notation: 6.25257 x 1013 km3
By Comparison: 57.723 x Earth
Metric: 102,410,000,000,000,000,000,000,000 kg
Scientific Notation: 1.0241 x 1026 kg
By Comparison: 17.148 x Earth
Metric: 1.638 g/cm3
By Comparison: 0.297 x Earth
Surface Area
Metric: 7,618,272,763 km2
English: 2,941,431,558 square miles
Scientific Notation: 7.6183 x 109 km2
By Comparison: 14.980 x Earth
Surface Gravity
Metric: 11.15 m/s2
English: 36.6 ft/s2
By Comparison: If you weigh 100 pounds on Earth, you would weigh 114 pounds on Neptune.
Escape Velocity
Metric: 84,816 km/h
English: 52,702 mph
Scientific Notation: 2.356 x 104 m/s
By Comparison: By Comparison: 2.105 x Earth.
Sidereal Rotation Period (Length of Day)
0.671 Earth days
16.11000 hours
By Comparison: 0.67 x Earth
Effective Temperature
Metric: -214 °C
English: -353 °F
Scientific Notation: 59 K
Atmospheric Constituents
Hydrogen, Helium, Methane
Scientific Notation: H2, He, CH4
By Comparison: Earth atmosphere consists mostly of N2 and O2.
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Last Updated: 28 Apr 2014