Neptune

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Neptune
Venus Mercury Mars Minor Planets.		Jupiter Saturn Uranus Pluto

DATA

Distance from the SUN	Mean: 4496.7 million Km (30.058 au.) Max: 4537 million Km (30.316 au.) Min: 4456 Km (29.8 au.)
Sidereal period	164.8years (60190.3 days)
Syodic period	164.8 days
Rotation period	16.1h
Mean orbital velocity	5.43 Km/sec
Axial inclination	28deg 48min.
Orbital inclnation	1deg 34min 19 sec 08
Diameter	Equatorial: 50538 Km Polar:49600 Km
Apparent Diameter from Earth	max : 2 sec .2 min: 2 sec .0
Reciprocal Mass (Sun = 1)	19300
Density (water =1)	2.0643
Mass (Earth = 1)	17.2
Volume (Earth = 1)	57
Escape Velocity	23.9 km/sec
Surface gravity (Earth = 1)	1.2
Mean surface temperature	-220 °C
Oblateness	0.02
Albedo	0.35
Max Magnitude	+7.7
Mean Diameter of Sun as seen from Neptune	1min 4sec

Opposition Dates

Date

30 July 2001

2 August 2002

4 August 2003

6 August 2004

8 August 2005

Description.

Neptune was discovered in I846 by astronomers puzzled by the irregular motion of Uranus, which in the end predicted the position of Neptune. At the time it almost doubled the size of the solar system as Neptune is such a distance from the Sun. Neptune has a faint ring system but it cannot be seen from Earth. Neptune orbit is almost perfectly circular, only Venus has a more circular orbit. Neptune is the 8th planet but because Pluto's orbit is very eccentric, it passes inside Neptune orbit for about 20 years out of every Plutonian orbit.

Satellites.

Neptune has 8 known satellites; Voyger 2 discovered the six inner ones in 1989. The six inner satellites are all very small (about 200 km) and cannot be seen from Earth. Triton, the seventh satellite, is the largest and is geologically active with volcanoes spewing material many Kilometers into space. It has a thin atmosphere of nitrogen. The outermost satellite is Nereid which is about 340 km in diameter.