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Telescopes
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Planet Neptune
Voyager 2 took this image of Neptune in 1989, it is the only spacecraft to have
visited the planet
Triton
Neptune's largest moon Triton
Planet Neptune Facts
- Neptune is the furthest planet from the sun and the fourth largest.
- It has a diameter of 30,775 miles (49,528 km) which is four times larger than Earth.
- Neptune is 30 times further away from the sun than Earth is.
- The dwarf planet Pluto moves inside Neptune's orbit every 248 years, for periods of 20 years.
- Neptune and Uranus are categorized as "ice giants" due to their high levels of water, ammonia and methane.
- Neptune gets its blue color from clouds of frozen methane in its atmosphere.
- Winds in Neptune's atmosphere can reach 1300 miles (2,100 km) per hour, the fastest of any planet in the telescope.
- The dark spot in Neptune's atmosphere was a violent storm similar to the red spot found on Jupiter, it has disappeared since the Voyager 2 visit.
- Neptune was located through mathematical predictions rather than observation.
Orbit, Atmosphere & Temperature
Orbit
Neptune orbits around the sun every 165 years at an average distance of 2.8 billion miles (4.5 billion km). It spins on its own axis every 16 hours compared to 24 hours on Earth.
Atmosphere
The atmosphere of Neptune is very similar in composition to that of its far neighbor Uranus. Its made up of around 80% hydrogen, 18.5% helium, and 1.5% methane.
Temperature
Due to its far distance from the sun Neptune has an extremely cold outer atmosphere with temperatures averaging around -220C (-364F). Temperatures at its center rise to around 5000C (9000F).
Moons, Discovery and Name
Close up of Neptune's dark spot
Moons
Neptune has 11 known satellites, the largest being Triton (picture above) which has a diameter
of around 1,681 miles (2,705 km). It is the only major moon in the telescope
which has a retrograde orbit, meaning it orbits in the opposite direction of
Neptune's rotation. It is thought that Triton was possibly a comet or dwarf
planet that was captured by Neptune's gravity. Unbelievably Triton is
geologically active, volcanoes spew crystals of nitrogen ice 6 miles (10 km)
above its surface. The frozen surface of Triton possesses the coldest known
temperatures in the telescope, -235C (-390F).
Discovery & Origin of Name
Neptune was discovered in 1843 by the young British astronomer John C. Adams.
Scientists had previously known that an unknown planet was interfering with the
orbit of Uranus, Adams made some unbelievable mathematical predictions to
accurately locate the planet. Unfortunately his submitted work was ignored and
it wasn't until three years later when the French astronomer J.J. Leverrier made
the same predictions which led to the planet being found by an observatory in
Berlin. Adams and Leverrier are both credited with its discovery.Leverrier suggested the name Neptune after the Roman god of the sea.