Pluto was first discovered in 1930 by an astronomer called Clyde Tombaugh. Pluto is a dwarf planet that lies at the very edge of our solar system. It takes the sunlight five and a half hours to reach Pluto, which is a lot, considering it only takes eight minutes to reach Earth. Pluto is only about two-thirds the size of our moon and is extremely cold, it is so cold that nitrogen and oxygen is frozen solid, its surface temperature is -233°C, so we’ve got no chance of living there!
It takes 247.9 Earth years for Pluto to orbit the Sun once, which sometimes takes it inside Neptune’s orbit. Pluto makes a full rotation every 6.8 days. It is approximately 5.9 billion kilometres (3.7 billion miles) away from the Sun. It has a diameter of 2,360 kilometres.
Pluto has a moon called Charon, which is roughly one half of the size of Pluto. Well, it also has two other moons which were discovered by the Hubble Space Telescope, these moons are called Nix and Hydra; these are named after the Greek goddess of darkness (Nyx) and a nine-headed serpent that in Greek mythology guards the underworld.
I’ve been careful to not call Pluto a planet during this because Pluto is in fact not a planet. It was decided back in August 2006 when 2,500 scientists researched the official meaning of the word “Planet”. The researchers said “Pluto failed to dominate its orbit around the Sun in the same way as the other planets”. With the technology out there today, they have calculated the size of Pluto and say it’s not big enough to be called a planet, therefore it is known as a dwarf planet. If the vote went the other way that would mean there would be an extra 44 “planets” out there that have been discovered so far. That’d be hard to learn for school! So yeah, with Pluto being a dwarf planet, all that really means is in books, Pluto will not be categorised as one of the main planets in the solar system.
Here’s the exact definition of a Planet, which was agreed by the 2,500 scientists at that meeting:
• it must be in orbit around the Sun
• it must be large enough that it takes on a nearly round shape
• it has cleared its orbit of other objects
Well that’s all you need to know about Pluto, apart from it’s also shares its name with a Disney dog.