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    Neptune was not known to the ancients.  Instead, it was discovered by Johann Galle in 1846.  The planet was named with the same sort of idea, after the Roman gods.  Neptune was the Roman version of the Greek god Poseidon, god of the sea.  Both Neptune and Uranus appear as pretty little bluish points, slightly larger than a star.


Mass -- 1.0244 x 1026 kg   (17.147 earth masses)


Radius -- 15,388 mi   (24,764 km or 3.883 earth radii)


Distance from the sun (average) -- 2,795,084,800 mi   (4,498,252,900 km or 30.069 AU)


Gravity -- 35.14 ft/sq. sec   (10.71 m/sq. sec)

    An adult weighing 140 lbs on Earth would weigh 153 lbs on Neptune.


Orbital velocity -- 12,253 mph   (19,720 km/hr or 0.490 earth speed)


Orbital eccentricity -- 0.00859

    This is how off-circular the moon's orbit around the Earth is.  An eccentricity of 0.00 would be a perfect circle.  An eccentricity of nearly 1 would be a very flattened oval.  For a fun project on ellipses and eccentricity, click here.


Sidereal rotation -- 16.11 hr   (0.673 earth days)

    A day on Neptune would be equivalent to less than 3/4 Earth days.


Sidereal orbit -- 1,444,560 hr   (60,190 earth days or 164.8 earth years)

    Neptune's year is 165x the length of Earth's year.


Moons -- 13, the largest of which is Triton



For more information on Neptune, please visit SEDS' website and NASA's website  Both websites are wonderful resources.


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Website last updated March 16,  2006.  Hosted by Anthony Watts, KMXI Radio.  Webmasters Tiara Norris and Brendan Diamond.