Triton is extremely cold, with surface temperatures around minus 391 degrees Fahrenheit (minus 235 degrees Celsius). Triton is the only large moon in the solar system that circles its planet in a direction opposite to the planet's rotation (a retrograde orbit), which suggests that it may once have been an independent object that Neptune captured. Since Neptune was named for the Roman god of the sea, its moons are named for various lesser sea gods and nymphs in Greek mythology. Neptune's largest moon Triton was discovered on October 10, 1846, by William Lassell, just 17 days after Johann Gottfried Galle discovered the planet. This means that Neptune experiences seasons just like we do on Earth however, since its year is so long, each of the four seasons lasts for over 40 years. Neptune’s axis of rotation is tilted 28 degrees with respect to the plane of its orbit around the Sun, which is similar to the axial tilts of Mars and Earth. This repeating pattern prevents close approaches of the two bodies. Pluto can never crash into Neptune, though, because for every three laps Neptune takes around the Sun, Pluto makes two. This switch, in which Pluto is closer to the Sun than Neptune, happened most recently from 1979 to 1999. Pluto's highly eccentric, oval-shaped orbit brings it inside Neptune's orbit for a 20-year period every 248 Earth years. Sometimes Neptune is even farther from the Sun than dwarf planet Pluto. And Neptune makes a complete orbit around the Sun (a year in Neptunian time) in about 165 Earth years (60,190 Earth days). One day on Neptune takes about 16 hours (the time it takes for Neptune to rotate or spin once). Credit: NASA Visualization Technology Applications and Development (VTAD) From this distance, it takes sunlight 4 hours to travel from the Sun to Neptune.Ī 3D model of Neptune, an ice giant planet. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth.

If Earth were the size of a nickel, Neptune would be about as big as a baseball.įrom an average distance of 2.8 billion miles (4.5 billion kilometers), Neptune is 30 astronomical units away from the Sun. With a radius of 15,299.4 miles (24,622 kilometers), Neptune is about four times wider than Earth. The temperatures, pressures, and materials that characterize this planet are most likely too extreme and volatile for organisms to adapt to. Neptune's environment is not conducive to life as we know it. The planet is named after the Roman god of the sea, as suggested by Le Verrier. Using predictions made by Urbain Le Verrier, Johann Galle discovered the planet in 1846. The ice giant Neptune was the first planet located through mathematical calculations.

The warm light we see here on our home planet is roughly 900 times as bright as sunlight on Neptune. Neptune is so far from the Sun that high noon on the big blue planet would seem like dim twilight to us. In 2011 Neptune completed its first 165-year orbit since its discovery in 1846. More than 30 times as far from the Sun as Earth, Neptune is the only planet in our solar system not visible to the naked eye. Here is a table of Neptune's Moons with additional information.Dark, cold, and whipped by supersonic winds, ice giant Neptune is the eighth and most distant planet in our solar system. There is an excellent resource for more information about Neptune's Moons on the NASA website. Particularly for the five outer moons, some of this information is conjectural, and subject to change. Triton is so much larger than the other moons that it makes up about 99.7% of the total mass of all the moons.īelow, a table lists the known moons, with information about their orbits and diameters. Unfortunately, for Triton, its orbit is decaying, and in the relatively near future, perhaps several million years, it will disintegrate, and could form a new, more distinct ring system. Triton is in a synchronous orbit around Neptune, meaning that, like our own Moon, the same side faces Neptune. It is the only large moon in the Solar System that has a Retrograde Orbit. It was once, possibly, a Kuiper Belt Object as it is very similar to Pluto. This leads astronomers to believe that it was captured long in the past, as virtually all natural satellites, formed along with their parent body, orbit in Prograde Orbits. Triton, the largest at more than 2,700 km in diameter, and the one first discovered soon after Neptune itself on October 10th 1846 by the English astronomer William Lassell, orbits in a Retrograde Orbit, in the opposite direction to most of the other moons.

Neptune has 14 identified moons, as at September 2013, named for minor water deities in Greek mythology.

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