Bob the Alien's Tour of the Solar System
Dwarf Planets Pluto Eris Ceres Naming Pluto Pluto's Moons Pluto's Rise and Fall New Horizons 11 Facts about Dwarf Planets

Eleven Facts about Pluto and Dwarf Planets

Fact One

All dwarf planets are smaller than all of the regular planets in the Solar System. The most famous dwarf planet, Pluto, is smaller than Earth's Moon, and half the width of Jupiter's moon, Ganymede.

Fact Two

Dwarf planets orbit on a different plane than the other 8 planets, going over them and below them.

Fact Three

The orbits of dwarf planets are elliptical, meaning that they are more oval than round. Pluto can sometime come closer to the Sun than Neptune, but then go almost two billion kilometres further away from Neptune's orbit. In the picture below, you can see Pluto's orbit (in grey) and Neptune's orbit (in blue).

Orbits of Neptune and Pluto

Fact Four

Pluto is the planet with the lowest pull of gravity in the Solar System. This will explain why its moon, Charon, orbits the planet so closely (at a distance of 19,640 kilometres).

Fact Five

Pluto's journey around the Sun takes 248 Earth years. Eris' journey takes 557 years. Pluto was discovered in 1930 which means that it won't be until 2117 until it has made a complete orbit of the Sun. Eris, discovered in 2005, will make a complete orbit of the Sun in 2562.

Fact Six

One of Pluto's moons, Charon, is not much smaller than Pluto itself. No other moon is as close to the size of its planet as Charon is to Pluto. (Pluto is 2,270 kilometres wide, Charon is 1,207 kilometres wide).

Fact Seven

New Horizons was a space craft that launched in 2006. Its mission was to fly past Pluto and its moons which it did in July 2015. When it was launched, Pluto was still recognised as a planet and was the only one not to have been visited by a space probe. Pluto lost its status as a planet in summer 2006, so New Horizons can no longer be recognised as the mission to visit the last planet in the solar system. The mission to be credited with that is Voyager, as Voyager 2 reached Neptune in 1989.

Fact Eight

Pluto was the only planet to have been discovered in the Twentieth Century, even though it is no longer recognised as a planet.

Fact Nine

Nobody knows what the atmospheres of Pluto and the other dwarf planets contain, or even if they have any atmosphere. Any atmosphere is most likely to contain nitrogen.

Fact Ten

A day on Pluto lasts for 6 days and 9 hours, on Eris for 8 hours, on Ceres for 9 hours, 5 minutes and on Haumea for 4 hours.

Fact Eleven

Pluto's moon, Nix, is named after the Greek goddess of darkness and night. But, in Greek mythology, her name is spelled "Nyx". To avoid getting the moon confused with an asteroid which has already been called Nyx, and because they couldn't be bothered to think of another name, the International Astronomy Union (the people that give planets and moons names) changed the spelling to "Nix", taking the Egyptian spelling of the name.

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Pluto and Dwarf Planets Statistics Table

Meaning of Name
Name in Foreign Languages
Average Distance from the Sun km / miles / A.U.
Comparison with Earth: 149,597,890 km / 92,955,820 miles / 1.000 A.U.
Closest Distance to the Sun (Perihelion) km / miles / A.U.
Comparison with Earth: 147,100,000 km / 91,400,000 miles / 0.983 A.U.
Farthest Distance from the Sun (Aphelion) km / miles / A.U.
Comparison with Earth: 152,100,000 km / 94,500,000 miles / 1.017 A.U.
Diameter across equator km / miles
Comparison with Earth: 12,756 km / 7,926 miles
Diagram showing planet's size compared to the size of Earth Sizes of Earth and Dwarf Planets compared
Circumference around equator km / miles
Comparison with Earth: 40,074 km / 24,901 miles
Mass kg
Comparison with Earth: 5,973,700,000,000,000,000,000,000 kg
Time to spin on Axis
Comparison with Earth: 23 hours, 56 minutes
Time to orbit the Sun Earth years
Comparison with Earth: 365 days, 6 hours
Distance dwarf planet travels to complete one orbit km / miles
Comparison with Earth: 924,375,700 km / 574,380,400 miles
Gravity (Earth = 1)
Escape Velocity km/h / mph
Comparison with Earth: 40,248 km/h / 25,009 mph
Temperature at Cloud Tops °c / °F  / K
Comparison with Earth's average temp: 15 °c / 59 °F / 288 K
Contents of Atmosphere
Known moons
Past Missions (including nationality and year of launch)None
Present Missions New Horizons (USA, launched 2006, due to arrive at Pluto in 2015
Proposed or planned MissionsNone

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