When astronomers reclassified Pluto in 2006, they didn't just create a new category — they created a club. Pluto stopped being the ninth planet and became the most famous member of a brand-new group called dwarf planets. Right now there are five officially recognised dwarf planets in our solar system, and each one is wonderfully strange.
There are five officially recognised dwarf planets: Pluto, Eris, Haumea, Makemake and Ceres. Four of them live in the Kuiper Belt beyond Neptune. Ceres is closer in — in the asteroid belt between Mars and Jupiter. Astronomers think there could be hundreds more dwarf planets still waiting to be officially classified.
The Roll Call — In Size Order
Here are the five dwarf planets, biggest to smallest:
| Dwarf planet | Diameter | Where it lives | Discovered |
|---|---|---|---|
| Pluto | 2,377 km | Kuiper Belt | 1930 |
| Eris | 2,326 km | Beyond Kuiper Belt | 2005 |
| Haumea | ~1,740 km (long axis) | Kuiper Belt | 2004 |
| Makemake | ~1,430 km | Kuiper Belt | 2005 |
| Ceres | 940 km | Asteroid Belt | 1801 |
1. Pluto — The King of the Kuiper Belt
Pluto is the biggest, brightest, and most famous dwarf planet. 2,377 km across. Five moons. A heart-shaped plain of ice. Ice volcanoes. A blue sky. And the only dwarf planet ever visited by a spacecraft from Earth.
Pluto lives in the Kuiper Belt, about 5.9 billion km from the Sun. A year there lasts 248 Earth years. It was reclassified as a dwarf planet in 2006 — 76 years after it was first discovered as the "ninth planet." Read all about Pluto.
2. Eris — The One That Started Everything
Eris was the discovery that changed everything. When American astronomer Mike Brown spotted it in 2005, it looked like he'd found the tenth planet. Eris is 2,326 km across — very nearly the same size as Pluto, but actually slightly heavier.
The discovery forced astronomers to make a hard choice: either Eris (and possibly dozens more like it) had to be called planets, or Pluto had to lose its planet status. In 2006, they chose the second option — and the dwarf planet category was born. Eris is named after the Greek goddess of strife and discord, because that's exactly what its discovery caused among astronomers. More on the 2006 reclassification.
3. Haumea — The Egg-Shaped Spinner With Rings
Haumea is the weirdest dwarf planet of all. It is not round. It is shaped like an American football (a rugby ball). Why? Because it spins so fast that its own gravity can't keep it perfectly spherical — one full rotation takes just four hours, the fastest of any object its size in the solar system.
Haumea has two small moons, called Hi'iaka and Namaka, and even a small ring. It was discovered in 2004 and named after the Hawaiian goddess of childbirth. Its nickname during discovery was "Santa," because the team that found it first spotted it shortly after Christmas in 2004.
4. Makemake — The Easter Island Dwarf
Makemake (pronounced MAH-keh MAH-keh) is the fourth-largest dwarf planet, about 1,430 km across. It lives in the Kuiper Belt and is named after the creator god of the Rapa Nui people of Easter Island. Makemake has a copper-red colour, similar to Pluto, and it has one small moon called MK-2 that was found by the Hubble Space Telescope in 2016.
Makemake is so far from the Sun that one year there lasts about 306 Earth years. Like Pluto, its surface is mostly covered in frozen methane and nitrogen.
5. Ceres — The Closest Dwarf Planet
Ceres is the dwarf planet you might not expect — because it isn't out beyond Neptune. It is right in the middle of the asteroid belt between Mars and Jupiter, only about 414 million km from the Sun.
Ceres is the smallest dwarf planet at 940 km across, but it was actually the first one ever discovered — way back in 1801 by Italian astronomer Giuseppe Piazzi. For 50 years it was considered the eighth planet of the solar system. Then it was downgraded to an asteroid. Then, in 2006, it was upgraded again to dwarf planet status.
In 2015, NASA's Dawn spacecraft arrived at Ceres and orbited it for several years — making Ceres the first dwarf planet to ever have a long-term spacecraft visitor. Dawn found bright salt deposits, signs of a possible underground ocean, and surface features named after agricultural gods from many different cultures.
If you lined up all five dwarf planets next to each other, Pluto and Eris would be twins, Haumea would be the rugby ball, Makemake would be the slightly smaller copper one, and Ceres would be by far the smallest — tucked in close to home while the others drift out in the cold dark.
Why There Probably Aren't Just Five
Astronomers think there could be hundreds of dwarf planets in our solar system — they just haven't been officially recognised yet. Strong candidates include:
- Quaoar — a Kuiper Belt object with two rings, named after a Native American creator god
- Sedna — one of the most distant known objects, with a 11,400-year orbit
- Orcus — sometimes called the "anti-Pluto" because it shares Pluto's orbital rhythm
- Gonggong — named after a Chinese water god, with one moon
The IAU could promote any of these to full dwarf planet status in the future. More on the Kuiper Belt.
Pluto. Eris. Haumea. Makemake. Ceres.
And the dark is still being mapped.
Read about why Pluto became a dwarf planet in 2006, the Kuiper Belt where most dwarf planets live, or jump back to the main Pluto facts page.
Frequently Asked Questions
How many dwarf planets are there?
There are five officially recognised dwarf planets in our solar system: Pluto, Eris, Haumea, Makemake and Ceres. Four of them live in the Kuiper Belt beyond Neptune; Ceres is closer in, in the asteroid belt between Mars and Jupiter. Astronomers think there could be hundreds more.
What is the biggest dwarf planet?
Pluto is the largest dwarf planet by diameter, at 2,377 km across. Eris is very close in size (2,326 km) but actually heavier than Pluto. Pluto is sometimes called the 'King of the Kuiper Belt' because of its size and brightness.
What is the smallest dwarf planet?
Ceres is the smallest officially recognised dwarf planet, at about 940 km across. It is also the closest to the Sun and the only dwarf planet not in the Kuiper Belt — it lives in the asteroid belt between Mars and Jupiter.
Why is Eris not a planet?
Eris isn't a planet for the same reason Pluto isn't: it hasn't cleared its orbit of other rocks. Eris orbits the Sun and is round (the first two of the IAU's three rules), but it shares its lane with many other icy Kuiper Belt objects. So like Pluto, it is a dwarf planet.
Has a spacecraft ever visited a dwarf planet?
Yes — two of them. NASA's Dawn spacecraft orbited Ceres from 2015 to 2018, becoming the first spacecraft to orbit a dwarf planet. NASA's New Horizons spacecraft flew past Pluto in July 2015, becoming the first spacecraft to visit a Kuiper Belt dwarf planet up close.