Pluto Facts

Pluto was once classified as the 9th planet in our solar system. Because it was so far out, we knew very little about it and the images that we had were just grey and blurred.

All of this changed when the New Horizons space mission did flybys around Pluto and we had the opportunity to see high resolution pictures as well as the fact that Pluto has 5 moons.

Pluto Dwarf Planet Profile

Discovered By:Clyde W. Tombaugh February 18th 1930
Diameter:2,372 km
Mass:1.31 × 10^22 kg (0.17 Moons)
Orbit Distance:5,874,000,000 km (39.26 AU)
Orbit Period:248.0 years
Surface Temperature:-229°C

Pluto was listed as a planet from 1930 until 2006. It is the second closest dwarf planet to our sun and was once thought to be the largest dwarf planet.

After the New Horizons mission, it was found that the dwarf planet Eris is actually just a bit larger.

Who discovered the planet Pluto?

Many seemed to be under the misunderstanding that Pluto was named for a cartoon character with the same name.

In reality, an 11-year old girl in England, named Venetia Burney, suggest that it be named after the mythological Roman god that was the match to the Greek character Hades, the god of the underworld.

Pluto was discovered in 1930 by an astronomer at the Lowell Observatory in Flagstaff, AZ.

Clyde Tombaugh found Pluto by accident when he was searching for an unknown planet that many called “Planet X.”

They thought that this unknown planet was causing disturbances in the orbits of Neptune and Uranus.

Tombaugh compared photographs and found a faint small spot that he thought had moved.

It was then that they classified Pluto as a planet and made the assumption that there really wasn’t any Planet X.

The 9th Planet

Over the years, the misunderstanding of the name created a rather deep affection for what was considered at that time to be our 9th planet.

In 2006, Pluto was downgraded to a dwarf planet and this caused outrage from people all over the world.

Children wrote letters to the IAU (International Astronomical Union) and specifically to astrophysicist Neil deGrasse Tyson, to register their complaints.

It does show that people had a connection with that little planet that was both wonderful and confusing.

Moons of Pluto

The discovery of the 5 moons of Pluto was thanks to the 2015 New Horizon space mission.

Named: Charon, Styx, Nix, Kerberos, and Hydra, Charon is the largest of these moons and tidally locked to Pluto.

This means that Charon has only one side that always faces Pluto. Our own moon is tidally locked to Earth and that’s why we always only see one side of the moon.

The Pluto-Charon relationship is also considered to be a binary system or double-dwarf planet.

Facts about Pluto

  • Pluto is in the Kuiper Belt, surrounded by small icy objects.
  • The Kuiper Belt is thought to have been formed early in the solar system’s development.
  • Many of the objects in the Kuiper Belt are called “plutoids.”
  • Pluto is only 2/3 the size of our moon and has a mass that is 1/6th that of our moon.
  • It takes Pluto 246.02 Earth years to complete its orbit around the sun.
  • Pluto has an orbit that is elliptical and inclined, similar Eris, one of the other dwarf planets.
  • When Pluto’s orbit gets nearer to the sun its icy surface begins to melt, then rise, then forms a thin atmospheric layer of nitrogen, methane, and carbon monoxide.
  • When Pluto moves away from the sun the gaseous atmosphere freezes again and falls back onto its surface.
  • Pluto rotates east to west and due to the tilt of its axis it rotates on its side creating extreme seasons.
  • Pluto has a reddish color and its moon Charon is a gray color.
  • The different surface colors of both Charon and Pluto show that they are made up of different materials.
  • Pluto’s moon Charon was discovered in 1978. The two moons of Nix and Hydra were discovered in 2005. In 2011 and 2012, two other moons, P4 and P5 were discovered by the Hubble Space Telescope.
  • In 2006, Pluto was reclassified as a dwarf planet after the IAU created a new definition for both a planet and a dwarf planet.
  • The amount of sunlight that hits Pluto is the same intensity as the moonlight hitting Earth.


  • What position of planet was Pluto once thought to be in our solar system?
  • Does Pluto have an atmosphere?
    only when it gets near to the sun
  • How many moons does Pluto have?
  • What mysterious planet was Clyde Tombaugh looking for when he accidently found Pluto?
    Planet X
  • What are Pluto and its moon Charon called?
    a binary system or double-dwarf planet
  • What mistake did a lot of people make in Pluto’s name?
    they thought it was named after a cartoon character