A long time ago, people who studied the stars noticed something interesting in the night sky. Some stars seemed to move around, unlike the others that stayed in place. These moving stars were actually planets! The first planets people knew about were Mercury, Venus, Mars, Jupiter, and Saturn. Later, with better tools, they found Uranus, Neptune, and Pluto too.
As scientists looked further into space, they found out that Pluto wasn’t alone out there. There were many other objects like Pluto beyond Neptune. This made scientists think that maybe not all of these objects should be called planets. So, in 2006, a group called the International Astronomical Union (IAU) decided to create a new category called “dwarf planets.”
For something to be a dwarf planet, it needs to do two things:
1. It must travel around the Sun.
2. It must be big enough for its own gravity to make it round or almost round.
Regular planets have to do one more thing: they need to clear their path of other space stuff. Dwarf planets don’t do this, which is why they are different. Right now, there are five dwarf planets we know about: Ceres, Pluto, Eris, Haumea, and Makemake.
Ceres was the first dwarf planet discovered way back in 1801. It’s in a place called the asteroid belt, which is between Mars and Jupiter. At first, people thought Ceres was a planet, but then they found more objects like it, so they changed its category. In 2006, Ceres became a dwarf planet. It’s the biggest thing in the asteroid belt and spins around once every 9 hours. It takes 4.6 years to go around the Sun. Ceres doesn’t have any moons or rings, but it does have a thin atmosphere with some water vapor. It’s the smallest dwarf planet and was visited by a spacecraft called Dawn in 2015.
Pluto was found in 1930 and was once called the ninth planet. But in 2006, it became a dwarf planet. Pluto is icy and takes 6.4 Earth days to spin around once. It takes a whopping 248 years to orbit the Sun! Pluto has a thin atmosphere and five moons, with Charon being the biggest. In 2015, a spacecraft named New Horizons visited Pluto and sent back amazing pictures.
Eris was discovered in 2005 and is named after a Greek goddess. When Eris was found, people thought it might be the tenth planet. It’s a bit smaller than Pluto but heavier and covered in ice. Eris has one moon called Dysnomia and is very far from the Sun, taking 558 years to go around it once.
Haumea is special because of its unusual shape. It spins really fast, completing a spin every four hours. Haumea takes 284 years to orbit the Sun and has ice on its surface. It has two moons named Hi’aka and Namaka and is named after a Hawaiian goddess.
Makemake was found in 2005 and is named after a creator god. It’s covered in ice and is very bright, second only to Pluto in its area of space called the Kuiper Belt. Makemake is about two-thirds the size of Pluto and has at least one moon.
Scientists think there might be hundreds more dwarf planets out there waiting to be discovered. As they keep exploring, we might find even more of these fascinating worlds.
In the end, learning about dwarf planets like Ceres, Pluto, Eris, Haumea, and Makemake helps us understand our Solar System better and shows us how exciting space can be!
