What is the Planet Neptune?
Neptune is the eighth and farthest planet from the sun. Neptune’s atmosphere gives it a blue color that matches the name of the Roman sea god. This means that it has the same gaseous surface as the gas giants, but has an interior that is mostly ice and rock. Neptune is slightly smaller than its sister planet Uranus, making it the 4th largest planet. However, Neptune is slightly more massive than Uranus, making it it becomes the 3rd largest planet by mass.
Highlights of Planet Neptune:
| Moons | 14 (and growing) |
| Mass | 17 times the mass of Earth |
| Diameter | 30,775 miles (49,528 km) |
| Year | 164 Earth years |
| Day | 16.1 hours |
| Average Temperature | minus 331°F (-201°C) |
| Distance from the Sun | 8th planet from the sun, 2.8 billion miles (4.5 billion km) |
| Type of Planet | Ice Giant (gas surface with an interior composed of ices and rock) |
The Atmosphere of Neptune
Neptune’s atmosphere is mostly hydrogen with a smaller amount of helium. Neptune’s surface swirls with large storms and strong winds. A large storm was captured by Voyager 2 as it passed Neptune in 1989. It’s called the Great Dark Spot. The storm is as big as the size of the Earth!
The Moons of Neptune
Neptune has 14 known moons. Neptune’s largest moon is Triton. Neptune also has a small ring system similar to Saturn, but not as large or visible.
How does Neptune compare to Earth?
Because Neptune is a gas giant, it doesn’t have a rocky surface to walk on like Earth. Also, Neptune is very far from the Sun, unlike Earth, it gets most of its energy from its inner core, not the Sun. Neptune is much larger than Earth. Although most of Neptune is made up of gas, its mass is 17 times that of Earth.
How do we know about Neptune?
Neptune was first discovered by mathematics. When astronomers discovered that the planet Uranus was not following their predicted orbit around the sun, they realized that there must be another planet pulling Uranus by gravity. They used a little more math and figured out the location of Neptune. In 1846, they were finally able to see Neptune through a telescope and check their calculations.
The only space probe to visit Neptune was Voyager 2 in 1989. Using close-up images from Travel 2, scientists were able to learn a lot about Neptune.
Interesting Facts about the Planet Neptune
There is still controversy about who discovered Neptune.
It is the coldest planet in the solar system.
The largest moon, Triton, orbits Neptune upside down relative to the other moons. This is called a retrograde orbit.
Despite its enormous size, the gravity on Neptune is similar to that on Earth.
It was the first planet discovered by mathematical prediction.