Pluto was the last of all the planets to be discovered, and it was only found because it has a slight effect on the orbits of Neptune and Uranus.
Pluto is the furthest out of all the planets, varying from 4730 to 7375 million km from the Sun.
The Sun is so far from Pluto that if you could stand on the planet’s surface, the Sun would look no bigger than a star in Earth’s sky and shine no more brightly than the Moon does.
Pluto’s orbit is so far from the Sun that it takes 248.54 years just to travel right around once. This means that a year on Pluto lasts almost three Earth centuries. A day, however, lasts just under a week.
Pluto has a strange elliptical (oval) orbit which actually brings it closer to the Sun than Neptune for a year or two every few centuries.
Unlike all the other planets which orbit on exactly the same plane (level) as the Earth, Pluto’s orbit cuts across diagonally.
While studying a photo of Pluto in 1978, American astronomer James Christy noticed a bump. This turned out to be a large moon, which was later named Charon.
Charon is about half the size of Pluto and they orbit one another, locked together like a weightlifter’s dumbbells.
Charon always stays in the same place in Pluto’s sky, looking three times as big as our Moon. 106 Planets
Unlike the other outer planets, Pluto is made from rock. But the rock is covered in water, ice and a thin layer of frozen methane. Daytime temperatures on Pluto’s surface are -220°C or less, so the surface is thought to be coated in frozen methane.
Pluto is tiny in comparison to the Earth, which is why it was so hard to find. Earth is five times bigger and 500 times as heavy. This illustration shows the relative sizes of the Earth and Pluto.
Pluto was discovered on 18 February 1930 by young American astronomer Clyde Tombaugh.