An image of Neptune made by Voyager 2 in August 1989. The Great Dark Spot, with The Scooter, a white patch just beneath it, are...Read More >>An image of Neptune made by Voyager 2 in August 1989. The Great Dark Spot, with The Scooter, a white patch just beneath it, are visible in the planet's southern hemisphere, on the left of the globe. Neptune is the eighth planet from the Sun—the most distant of the true planets. One of the gas giants—sometimes grouped with Uranus as one of the two "ice giants"—it is the fourth largest planet in the Solar System. Little was known about Neptune until Voyager 2 paid it a visit in 1989. The bluest planet in the Solar System, like Uranus it is almost completely featureless, although clouds and storms can sometimes be seen on its surface. Neptune has 14 known moons, with Triton, the only one that is spherical, rather than irregular, in shape, by far the largest.
Neptune was discovered by German astronomer Johann Galle in 1846. Noting that Uranus was being pulled slightly off course, astronomers concluded that the pull of gravity from another large planet farther away from the Sun was responsible. The new planet was located using mathematical calculations.
The first person to observe Neptune was Galileo, in 1612. But he mistook Neptune for a star. Galileo seems to have noticed that the "star" he saw had moved relative to the other stars around it.
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