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Neptune is generally the eighth planet from the Sun. At times, Pluto’s orbit crosses Neptune’s making Neptune the farthest planet from the Sun. Neptune is a gaseous planet and is the fourth largest gas planet. Jupiter, Saturn, and Uranus are larger. The existence of Mercury, Venus, Mars, Jupiter, and Saturn has been known for a long time. These planets can be seen and tracked fairly easily without a telescope. When Uranus was discovered in 1781, people thought that planet was the last in our solar system. After watching Uranus for 20 years, astronomers realized that a large object beyond Uranus was changing Uranus’s orbit. Astronomers thought another planet had to exist farther out than Uranus. Two Europeans, John Couch Adams and Urbain J. J. Leverrier, calculated where they believed the unknown planet should be. A German astronomer named Johann G. Galle identified it in 1846 based on Leverrier’s location calculations. The English and French agreed to name the new planet, Neptune, after the Roman god of the sea. Almost nothing was known about Neptune until the Voyager 2 space probe flew by the planet. Astronomers knew that the planet had two moons. In 1989, Voyager 2 found six more moons. It also detected high clouds of methane ice crystals. Neptune's most prominent feature is the Great Dark Spot (left) in the southern hemisphere. It is about half the size as Jupiter's Great Red Spot (about the same diameter as Earth). Neptune's winds blow the Great Dark Spot westward at 700 miles/hr (300 meters/second). Voyager 2 also saw a smaller dark spot in the southern hemisphere. A small irregular white cloud that zips around Neptune every 16 hours or so is now known as "The Scooter" (below). It may be a plume rising from lower in the atmosphere but its true nature remains a mystery.
Neptune’s magnetic field is 25 times greater than the Earth’s. Particles from the Sun called solar wind are captured by the magnetic field. Neptune is believed to have three parts: atmosphere(hydrogen, helium and methane), liquid hydrogen, and a rocky core. The planet appears blue in color due to the methane in the atmosphere. There is probably no dividing line between the atmosphere and the crust. The planet’s winds may be the strongest in the solar system, up to 1200 miles/hr (1,931 km/hr). Neptune has four very thin rings. These rings were spotted in 1984 when the planet passed in front of a star. In 1989, Voyager 2 confirmed that these rings existed. Triton, Neptune’s largest moon, is very interesting. It rotates in an opposite direction from Neptune’s rotation. It is the only moon to do this. Some scientists think Triton is an asteroid that was captured by Neptune. Triton also has the lowest recorded temperature in the solar system, -390o F (-234o C). Neptune Facts
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"The
Scooter"