Triton Facts for Kids
(Distance of the Moon from Earth 384,000 km/ 240,000 mi)
Diameter: 2700 km (1680 mi)
Day length & time to orbit Neptune: 5.9 Earth days
Note: These numbers have all been rounded.
Neptune's large moon Triton is a strange object. Astronomers have long thought that like Pluto, Triton could be a Kuiper Belt object, an icy body from the outer Solar System.
Neptune was discovered on September 23, 1846. Triton was discovered 18 days later.
In the 19th century astronomers realized that something was wrong with the orbit of Uranus. Some people thought the gravity of an unknown planet was disturbing it. French mathematician Urbain LeVerrier calculated the location of the new planet, and sent his prediction to Johann Galle at the Berlin Observatory. Galle found the planet the same night. English astronomer William Lassell discovered Triton soon afterwards.
Triton didn't have a name until 1949.
There was a lot of arguing about what to call the new planet, so it took some time for it to get a name. Once people agreed to name the planet after the Roman sea god, its moon didn't need a name. Everybody just called it Neptune's satellite. But when Gerard Kuiper discovered a second moon in 1949, he named it Nereid after the sea nymphs from mythology. He also called the large moon Triton after Neptune's son and messenger.
Neptune has 14 known moons, but Triton is by far the biggest.
If you added up the mass of all 14 moons, 99.7% would belong to Triton - that's almost all of it.
Both a day and a month are almost six Earth days long.
A day on Triton is the same length as its month. Like other moons, including ours, Triton turns once on its axis as it goes once around its planet. Neptune is bigger than Earth and its gravity is stronger, so Triton moves much more quickly than our Moon does.
Triton is the only large moon that orbits in the opposite direction to its planet's rotation.
The Solar System formed from a flat disk of material orbiting the the Sun. It's normal for Solar System objects to move in that same direction. But Triton doesn't, it moves in the opposite direction. We call an orbit like that retrograde. It shows that Triton didn't form along with Neptune – it is a captured object.
Triton has volcanoes.
Voyager 2 saw eruptions on Triton. The volcanoes don't throw out liquid rock. They are cryovolcanoes, ice volcanoes like those on Saturn's moon Enceladus.
Triton has polar icecaps, and is a reddish color.
Over half of Triton's surface is frozen nitrogen. Ihe icecaps aren't made of frozen water, but of nitrogen and methane. Ultraviolet light hitting the methane ice produces molecules called tholins which are red.
Triton has a very reflective surface and no atmosphere, so it's extremely cold.
Earth's atmosphere helps keep the planet warm. Triton has no atmospheric blanket, and its surface reflects most of the sunlight that it gets. It's the coldest body in the main part of the Solar System. The surface temperature averages only -235oC (-391oF). It's as cold as Pluto, sometimes colder.
Triton is different from the other moons, but it's very similar to Pluto.
Triton and Pluto are almost the same size, though Triton is slightly larger. They're both a reddish color. They're made of similar materials and have a similar density. (Density is how heavy something is for its size.) Astronomers think that Triton formed in the Kuiper Belt, but was captured by Neptune's gravity.
You can find out more about the Kuiper Belt by clicking on the link to "Kuiper Belt - Facts for Kids" below this article.
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Kuiper Belt - Facts for Kids
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