Sixteen Facts about Dwarf Planets
The dwarf planets are Ceres, Pluto, Haumea, Makemake and Eris. Here are some fascinating facts about these fascinating little worlds. Fascinating.
Pluto was once considered to be a planet
Pluto was classified as the ninth planet in the Solar System after its discovery in 1930, but it was reclassified as a dwarf planet in 2006 due to the discovery of other similar-sized objects in the Kuiper Belt.
Ceres was also once considered to be a planet
Initially discovered in 1801 by astronomer Giuseppe Piazzi, Ceres was classified as a planet. However, as more objects were found in similar orbits, it was reclassified as an asteroid and later as a dwarf planet when the category was defined in 2006.
Makemake was named after an Easter Island deity
The dwarf planet was discovered shortly after Easter in 2005, leading to its naming after the Rapa Nui god of fertility, Makemake. Before it got its official name, it was also nicknamed Easter Bunny by its discoverers.
Eris is denser and more massive than Pluto
Although slightly smaller than Pluto, Eris is more massive, which led to questions about Pluto’s classification as a planet
Ceres is situated in the asteroid belt
Ceres is the only dwarf planet located in the asteroid belt and was the first to be visited by a spacecraft, NASA’s Dawn mission.
Pluto has a large moon called Charon
Charon is so large relative to Pluto that they are sometimes considered a binary system, where both bodies orbit a point in space between them.
Eris has a very reflective surface
With a surface albedo of 0.96, Eris is one of the brightest objects in the Kuiper belt, reflecting most of the sunlight that hits it.
Haumea possesses a ring system
Besides having two moons (Hi?iaka and Namaka), Haumea is unique among dwarf planets for having a ring system, discovered in 2017.
Makemake's moon was discovered much later than the dwarf planet itself
Despite Makemake being discovered in 2005, its moon, MK 2, wasn’t discovered until 2015 due to its dark surface which is hard to detect
Haumea rotates exceptionally quickly
This elongated dwarf planet completes one rotation in under four hours, causing it to stretch into an ellipsoid shape due to centrifugal force.
Ceres shows signs of ancient water activity
Observations from the Dawn spacecraft have provided evidence that Ceres once had significant water activity, possibly an internal ocean.
Pluto’s heart-shaped feature is called Tombaugh Regio
This large, bright feature made of nitrogen and carbon monoxide ice is named after Pluto’s discoverer, Clyde Tombaugh.
Eris was informally called 'Xena' by its discovery team
The nickname, inspired by the television series Xena: Warrior Princess, was used internally by astronomers before the official name was decided.
Eris' discovery led to the definition of the term "dwarf planet."
The need to classify Eris and similar objects resulted in the IAU creating the new category in 2006, which also affected Pluto’s status.
New Horizons provided a close-up look at Pluto
Launched in 2006, NASA's New Horizons spacecraft flew by Pluto in July 2015, offering the first close-up images of its surface and moons.
Haumea and its moons originally had Christmassy names
Haumea was discovered shortly after Christmas 2004 by a team led by Mike Brown. They nicknamed it Santa. When they later discovered its too moons, these were nicknamed Rudolph and Blitzen before getting their official names: Hi?iaka and Namaka.
