Last Updated On: January 5, 2021

What is the temperature of pluto?

Pluto receives very little sunlight because it is so far from the Sun (5.9 billion kilometers or 3.7 billion miles), making the average temperature very low, about -229 °C (44 K).

What is the history of Pluto?

Initially, the American astronomer Percival Lowell proposed a ninth planet, who sought to explain Neptune and Uranus’s orbits’ irregular movements. Lowell believed that an unknown planetary body caused these gravitational changes.

Lowell made a rough estimate of this possible ninth planet’s location and searched for it, without success, for ten years. However, in 1929, W. H. Pickering used Lowell’s calculations to continue the search.

Pluto and Charon (illustration)

Finally discovered in 1930 by astronomer Clyde Tombaugh, Pluto was long considered the ninth planet in our solar system. However, in 2006, assuming that worlds very similar to Pluto were found in the Kuiper Belt, the IAU re-classified it as a dwarf planet.

During the 76 years that Pluto was considered a planet, and until its reclassification as a dwarf planet, it completed one-third of its orbit around the Sun.

Its name comes from the Roman god of the underworld. It was proposed by an 11-year-old student from England named Venetia Burney.

In its orbit, Pluto has five known moons, the largest being Charon. The moon Charon is so large that it reaches 50% the size of Pluto. It is the largest moon in our solar system, considering the size of the planet it orbits.

What is Pluto’s surface like?

Pluto’s composition

Pluto’s surface is mainly composed of craters, mountains, valleys, and plains. The hills can reach an altitude of 2 to 3 kilometers (6500 to 9800 feet) and are composed of frozen water. Valleys can reach a length of 600 kilometers (370 miles).

It is icy, which makes it very unlikely to be able to sustain life. The water, at Pluto temperatures, would be completely frozen.

The craters can reach a diameter of 260 kilometers (162 miles) and represent a point in Pluto’s landscape. It can be seen through photographs and research that erosion is causing an impact on the craters.

The Pluto Controversy

After its discovery, some astronomers questioned if Pluto really had the necessary mass to have any effect on the orbits of Neptune and Uranus. This changed in 1978 when Robert Harrington and James Christy discovered what would then be Pluto’s only moon, known as Charon.

At that time, it was also determined that the size of Charon was half that of Pluto, and so they named the composite system between Charon and Pluto as a “double planet,” with enough mass to have effects on the orbits of Neptune and Uranus.

What are the moons of Pluto?

Pluto has five moons known to the scientific community: Charon, Styx, Kerberos, Hydra, and Nix. This lunar system could have been formed by the collision between Pluto and other astronomical bodies at the beginning of time in our solar system.


Charon is the Pluto’s biggest moon.

It is Pluto’s largest moon, reaching 50% of its own size. It is located at a distance of 19,640 kilometers (12,200 miles). Pluto and Charon are so close, and they are referenced to as the double planet.

Charon’s orbit around Pluto takes about 153 hours, which is the same time it takes for Pluto to complete one rotation on its axis. It means that Charon is always located at the same point in Pluto’s sky. It doesn’t set or rise. This moon has no rotation on its axis, so it is always facing Pluto in the same way.

Pluto’s other four moons are much smaller than Charon, less than 160 kilometers (100 miles) wide. They have an irregular shape, and unlike other moons in our solar system, they have their own rotation on their axis, so they do not maintain the same position towards Pluto.

Pluto: rotation and orbit

As for its rotation, a day on Pluto takes approximately 153 hours. Its axis of rotation inclines 57 degrees. Like Venus and Uranus, Pluto exhibits a retrograde orbit.

Pluto makes a full rotation around the Sun in 248 years. Its oval orbit can take it as far as 4.5 billion kilometers (2.81 billion miles) from the Sun.

Important Facts


Pluto is composed of ⅓ water in the form of ice, which is more than the entire amount of water that exists in the Earth’s oceans. The remaining surface is composed of rocks.

Smaller than some moons

Pluto is smaller than some moons in our solar system. It is smaller than Triton, Europa, Io, Callisto, Titan, Ganymede, and our planet’s moon.


New Horizons passing by Pluto (illustration)

Pluto has been visited by the New Horizons spacecraft, which was launched in 2006. It passed near this dwarf planet on July 14, 2015, a moment that was used to take pictures and make measurements. With only the size of a piano, weighing about 453 kilograms (1,000 pounds) and a budget of 700 million dollars, it reached Pluto in a journey of 9 years and 3 billion miles.

Young assistant

Clyde Tombaugh

When Clyde Tombaugh got the first photographic evidence of what was then called the ninth planet, he was only 24 years old. He was only an assistant at the Lowell Observatory in Arizona. Tombaugh’s ashes are aboard the New Horizons spacecraft, which is currently en route to the Kuiper Belt.


Disney’s dog Pluto was named this way in the same year that the (current) dwarf planet was discovered. Initially, it was thought that the cosmic object had this name because of Disney’s dog, but it was vice-versa.

Kuiper Belt

Pluto is the brightest member of the Kuiper Belt, a mass of objects orbiting the Sun beyond Neptune.

Ring system

At least one research suggests that space debris floats around Pluto, which could form a ring system. It wouldn’t be a big surprise if this were validated since the scientific community knows of at least one ringed asteroid.

An elevator is possible

Space elevators have always been an important source of science fiction. Pluto and Charon’s unique features, which always show the same face, would make possible the installation of such a device, which could join the two planetary bodies without using spaceships.