Neptune Facts

Neptune Planet Profile

Distance from Sun: 2.793 billion mi
Radius: 15,299 mi
Polar Diameter: 48,682 km
Orbital period: 165 years
Mass: 1.024 × 10^26 kg (17.15 M⊕)
Moons (14, including Triton)
Date of Discovery: September 23, 1846 by Urbain Le Verrier & Johann Galle

Neptune has a blue color and it is this color that was used to give it the name of the Roman god of the sea.

As the eighth planet from the Sun, it is listed as the last in our Solar System. Neptune is the 4th largest planet in diameter and third largest in mass.

Who discovered Neptune

Giving credit for the official discovery of Neptune is often debated as there are a few that feel they deserve credit. John Couch Adams, an English astronomer, submitted his findings for an unknown planet in 1845, but wasn’t taken seriously by the Royal Society.

John Couch Adams

The next year, Jean Joseph LeVerrier, a French astronomer submitted similar information to Adams and it was then that the Royal Society began to consider the additional planet as a possibility.

A third astronomer, Johann Gall, of Germany submitted even more detailed calculations for a new planet.

Eventually, LeVerrier was credited for the planet’s discovery, and this created a hot dispute until both LeVerrier and Adams were given credit.

The Blue Planet

Very little has been known about the blue planet way out in space until 1989 when the Voyager 2 spacecraft did a fly-by.

It was during this mission that they discovered Neptune’s rings, rotation, atmosphere, and the number of moons.

Voyager 2 specifically gathered information on the features of one of the moons, Triton.

Very similar to the planet Uranus, Neptune’s upper atmosphere is made up of mostly hydrogen (80%), helium (19%), and trace amounts of the methane that gives it the blue coloring.

Neptune has a much deeper shade of blue that makes it different than Uranus in atmospheric composition.

Neptune’s active climate

The Voyager 2 mission discovered that Neptune has “Dark Spots,” which are large storms somewhat like Jupiter’s Great Red Spot.

Thanks to the Hubble Space Telescope, we know that Neptune’s storms have shorter lifespans. Voyager 2 also found two additional weather patterns of a fast-moving white storm system that was given the nickname of “Scooter.”

This storm is short-lived and also smaller than the Dark Spots.  Since Neptune is a gas giant it shares the same characteristic of having its atmosphere divided into two latitudinal bands with high wind speeds up to 600 m/s.

This gives Neptune the distinction of having the fastest known wind speed in the solar system.

The Surface of Neptune

The inside of Neptune is also close to Uranus as it has two layers: a rocky core that is thought to be about 1.2 times Earth’s mass, and a hot and dense liquid mantle made of water, ammonia, and methane that is from 10-15 times the Earth’s mass.

Uranus and Neptune share some similarities but are distinctly different in the way that they emit heat.

Uranus emits about as much heat as it gets from the Sun, whereas Neptune emits almost 2.61 heat that it receives.

Although both planets have about the same surface temperature, Neptune only gets 40% of the energy from the Sun that Uranus receives. It is this additional internal heat that powers the wind speeds in the upper atmosphere.

Neptune’s Moons

Due to the rotation and size, a Neptune year is around 165 Earth years.

Neptune rotates very quickly and has the third shortest day in the Solar System.

Neptune is currently known to have 14 moons, with Triton being the largest and having a spherical shape.

Scientists believe that Triton was originally a dwarf planet that Neptune’s gravity caught and may explain why Triton’s rotation is opposite of Neptune’s.

Facts about Neptune

  • Neptune’s three major rings are so dim that until the Voyager 2 mission, they were thought to be incomplete rings. They are fainter than any of the other gas giants.
  • Neptune’s gravity is the second largest of any planet in the Solar System.
  • Neptune’s orbit path is nearing thirty times the distance of the Earth to the Sun.
  • The Great Dark Spot storm on Neptune is around the size of the Earth and the Small Dark Spot storm is nearing the size of Earth’s moon.
  • This moon Triton was discovered only 17 days after the planet was discovered.
  • Triton is listed as the coldest known object in the Solar System, with a surface temperature of -235 degrees C.

Neptune Quiz

  • Astronomy for Kids