Neptune
Mythology
Neptune was found in 1846 when astronomers were trying to find out what was causing small irregularities in Uranus’ orbit. They theorized another planet, and it was there. It turns out that this was blind luck, because Neptune is too far away from Uranus to affect it too much. Neptune is 4,497 million km (30 AU) from the sun and is named after the Roman god of the sea, who was known as Poseidon by the Greeks.
 Facts
Neptune has a very circular orbit, which is something that Pluto does not have. In fact, Pluto’s elliptical orbit actually made Neptune the farthest planet until a few months ago (March 1999). Neptune, the last gas giant, is a decent rotator. One day is 19.2 hours, but a year in Neptune is the same as 165 Earth years. Neptune is the smallest gas giant as well, with a diameter of 49,528 km (3.8 Earth diameters).
Viewing Neptune
This is a bit harder than finding Uranus. To find Neptune you need an even bigger telescope and a star chart, because Neptune is 8th magnitude, which is too faint to be seen by the naked eye. Neptune has 8 known satellites, and all but two were founded by Voyager 2 when it flew by. Triton, Neptune’s largest moon, is interesting because it has an atmosphere and is still geologically active.
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