We all know about Pluto, the former 9th planet in our solar system that was relegated down to the status of a dwarf planet. However, the other dwarf planets are rarely acknowledged despite them being just as fascinating as their larger planetary counterparts! So what separates dwarf planets from planets? While both circle the sun, dwarf planets are much smaller than regular planets. Dwarf planets are too small to have a strong enough gravitational force that would pull in all the material present in their orbits. There are currently five officially recognized dwarf planets in our solar system, including our infamous Pluto.
Ceres is the dwarf planet that is closest to the Sun with a distance of 257 million miles away, and it resides in the asteroid belt between Mars and Jupiter. Its revolution around the sun takes 4.6 years. With its width of 952 kilometers, it is the smallest dwarf planet out of the five. However, it is the largest object in the asteroid belt, making up one-third of the entire belt’s mass. Ceres has a solid core with an icy mantle and a rocky crust. 25% of its mass is made up of ice, and there are potentially underground oceans residing underneath its surface.
Ceres was first discovered in 1801 by Giuseppe Piazzi, and for quite a long time it was classified as an asteroid. However, due to its larger size and spherical shape, it was reclassified as a dwarf planet in 2006. It is the first dwarf planet to be visited by a spacecraft after NASA’s spacecraft Dawn entered its orbit in 2007.
The former ninth planet of the solar system Pluto is the second closest dwarf planet to the sun, being 3.7 billion miles away from it on average. Due to the angle of Pluto’s orbit, this number isn’t consistent and varies depending on the location of its orbit Pluto is in at the time. Its revolution around the Sun takes 248 years. Pluto’s width is 2380 kilometers, making it almost tied with Erist as the largest dwarf planet.
Pluto is mainly made of ice, which is comprised of frozen nitrogen, methane, and carbon dioxide. It potentially has a rocky metal core and underground ocean systems. Pluto has a thin atmosphere made of nitrogen, methane, and carbon monoxide. Pluto has five moons, and its biggest, Charon, is half of its size leading to them both orbiting each other to a certain extent.
Pluto was discovered in 1930 and established as the 9th planet in the solar system. This was brought under questioning in the 1990s, until its status was finally changed to a dwarf planet in 2006. NASA’s aircraft New Horizons passed by Pluto in 2015, nine years after its launch. New Horizons’ images are the source of most of the information we have on Pluto.
Haumea is 7.5 billion kilometers away from the Sun and takes 285 years to complete its revolution. It was discovered in 2004 and recognized as a dwarf planet in 2008.
Haumea has an oval shape, which is caused by its shape being distorted due to having an extremely quick rotation of only four hours. Haumea is made of rock with a coating of ice and has rings encircling it. Haumea has two known moons.
Makemake is 7.8 billion kilometers away from the Sun and takes about 305 years to complete its revolution. Makemake was discovered in 2005, months after the discovery of Eris. It was the discovery of these two celestial objects that led to astronomists establishing dwarf planets as a category.
Makemake has frozen methane and ethane on its surface. Its surface is scattered with pellets of frozen methane. Makamake potentially has a thin atmosphere made of nitrogen.
Eris. The dwarf planet has one single moon.
Eris is the farthest dwarf planet from the Sun at a distance of 10 billion kilometers away. It takes Eris 557 years to finish one whole rotation around the Sun. Eris is around the same size as Pluto, and its discovery in 2005 is what eventually led to the separate category of dwarf planets.
Eris has one small moon. It's estimated by scientists that Eris’ surface is similar to that of Pluto’s. Eris’ atmosphere freezes and collapses into its surface when furthest from the Sun. When getting closer to the Sun during orbit, the atmosphere sublimates straight from solid to gas.
Dwarf planets are among the fascinating astronomical objects in our solar system. Since there is so little known about the ones far away, there is much for us to learn about what makes every dwarf planet unique. While there are only five officially recognized dwarf planets in our solar system so far, there are many more celestial bodies that can potentially fall under the dwarf planet umbrella. As time goes on, our knowledge about the different dwarf planets will continue to grow.