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18/02/26
Pluto Day
On the 18th February every year it is Pluto Day; a day all about Pluto! It is a day commemorating the day Pluto was discovered in 1930.
An American astronomer called Clyde Tombaugh discovered Pluto through a telescope on the 18th February 1930.
He, with some other astronomer’s, were searching for a planet they believed existed beyond Neptune. When they were looking for it they named the mysterious planet “Planet X”.
Once discovered the planet needed an official name. An 11-year-old girl called Venetia Burney was having breakfast in England with her mother and grandfather. They were all reading the newspaper. Venetia’s grandfather wondered what the new planet would be called and Venetia said “Pluto”. This was after the Roman god of the underworld, which is fitting for a planet so far away and cold.
Her grandfather knew some astronomers so he mentioned it to them and they sent a message across to America. That is how an 11-year old English school girl from Epsom in Surrey named a planet!
10 Facts about Pluto
1. Pluto used to be the 9th planet in the Solar System but in 2006 it was changed to a dwarf planet. This is because other similar sized ‘planets’ were discovered called Ceres, Eris, Haumea and Makemake and it was decided they were all too small to be called planets and should be dwarf planets instead.
This meant Pluto was changed from a planet to a dwarf planet. It is very small and like most of the other dwarf planets it is part of the Kuiper Belt. This is a ‘belt’ of ice and other objects beyond Neptune. It was decided a dwarf planet would be ‘an object in orbit around the Sun that is large enough to pull itself into a nearly round shape but has not been able to clear its orbit of debris’.
2. Pluto is incredibly far away from us and the Sun. It is so far away it takes Pluto 248 Earth years for it to orbit the Sun just one time. Since it was discovered in 1930 it hasn’t fully gone round the Sun once, it still has 152 Earth years to go!
3. Pluto spins around very, very slowly. A single day on Pluto lasts 153 hours which is longer than 6 Earth days.
4. As it is so far away from the Sun temperatures are extremely low. It is thought to be as cold as -228°C to -238°C.
5. The planets orbit the Sun in an almost perfect circle. But Pluto has an elliptical orbit, which means its orbit is oval shaped. At times this means Pluto’s orbit crosses Neptune’s and is sometimes closer to the Sun than Neptune. This last happened between 1979 to 1999.
6. Pluto is so small it is actually smaller than our Moon.
7. Pluto has a rocky core covered in a thick mantle of ice and frozen gases such as methane, nitrogen, and carbon monoxide. It has a thin atmosphere that changes depending on how close it is to the Sun.
9. Pluto is orbited by five moons that we know about. The largest is called Charon and it is actually about half the size of Pluto. Pluto and Charon are often called a “double dwarf planet.” Pluto’s other moons are called Styx, Nix, Kerberos and Hydra.
10. The only spacecraft to ever explore Pluto up close was NASA’s New Horizons. It flew by the dwarf planet and its moons in 2015. It got the first close up photos of the dwarf planet and showed it has a heart-shaped glacier on its surface.
All photos and illustrations in this blog post are Whizzbots and Public Domain Images.