How Many Dwarf Planets Are There?

The five official dwarf planets

Each of the five has a different home. Ceres lives in the asteroid belt between Mars and Jupiter, and NASA calls it the only dwarf planet in the inner Solar System. Pluto, Haumea and Makemake sit in the Kuiper Belt, a doughnut-shaped region of icy bodies beyond Neptune. Eris orbits far beyond Neptune on a path that extends well past the Kuiper Belt. Each one has its own profile, including Ceres, which NASA's Dawn spacecraft orbited from 2015 to 2018.

Widths follow the Planetary Society's summary of the five. Haumea is stretched by its fast spin, so its longest axis is much larger than its other dimensions.

How the list grew from three to five

The category did not exist before August 2006, and it grew in steps.

• 2006: The IAU creates the dwarf planet category. Ceres, Pluto and Eris are the first members, according to a NASA JPL release from September 2006.
• June 2008: The IAU introduces the word "plutoid" for dwarf planets that orbit beyond Neptune. Only Pluto and Eris are named plutoids at that point.
• September 17, 2008: The IAU names Haumea as the fifth dwarf planet. The list is now Ceres, Pluto, Haumea, Eris and Makemake.
• February 2020: The Planetary Society counts five trans-Neptunian objects proven round and six more whose roundness is virtually certain. It says there are definitely at least 30, and possibly more than 100.
• November 10, 2026: A public list kept by Caltech astronomer Mike Brown shows 10 objects he calls nearly certain, plus hundreds of weaker candidates.

How did Haumea and Makemake get in without a spacecraft visit? The IAU's 2008 plutoid announcement gives the answer. For naming purposes, any body beyond Neptune with an absolute magnitude brighter than +1 is treated as a plutoid. Absolute magnitude is a measure of how bright an object would look at a standard distance, and brighter objects tend to be bigger, so the cutoff works as a rough size screen. If later work shows that an object does not qualify, it keeps its name but moves to another category. The same announcement says Ceres is not a plutoid because it lies in the asteroid belt, and that it is the only object of its kind. Eris was among the first two plutoids.

The leading candidates

Mike Brown sorts candidates into five groups using size and composition. His page, dated November 10, 2026, counts 10 nearly certain, 19 highly likely, 24 likely, 74 probable and 1,301 possible dwarf planets. The 10 nearly certain objects include four officially recognized worlds beyond Neptune (Pluto, Eris, Haumea and Makemake), five well-known candidates and one object known only by a provisional designation.

His thresholds rest on two facts. Ceres, at about 900 km (560 miles), is the only known round asteroid, so he uses roughly 900 km as the cutoff for rocky bodies. Saturn's moon Mimas, at about 400 km (250 miles), is the smallest generally round icy body, so 400 km is his lower limit for icy ones.

The Planetary Society's 2020 page names the same five, plus an object called 2002 MS4, as candidates whose roundness is virtually certain though not yet proven.

Why the count is not a fixed number

Several things keep the total moving.

Official status needs a decision. NASA's page still lists five. The IAU says there may be many more, perhaps more than a hundred, waiting to be discovered, but a candidate stays a candidate until the IAU acts.

Roundness is hard to prove. The Planetary Society says there are almost certainly more dwarf planets, but most are very far away and astronomers cannot yet show that they are round. Roundness is a key requirement.

Sizes are estimates. Brown notes that most sizes on his list come from absolute magnitude and an assumed reflectivity, and that he leaves out error bars. A wrong guess about reflectivity can shift a size a lot. Eris is the classic case: its size was first overestimated, then settled near 2,326 km (1,445 miles).

New objects keep arriving. Surveys keep finding faint bodies beyond Neptune, and each find can move a total up or down. For how such objects are spotted, confirmed and reported, see how minor planets are discovered.

A note for anyone who takes up stargazing after reading this: never point binoculars or a telescope at the Sun without a proper solar filter made for that purpose.

Common mistakes and myths

• Myth: Sedna, Gonggong, Quaoar and Orcus are already dwarf planets. They are not on NASA's list as of November 2026. Astronomers such as Brown call them nearly certain candidates, which is a judgment about their likely shape, not an IAU decision.
• Myth: the number is fixed at five. Five is a snapshot. It was three in 2006, and it has been five since 2008.
• Myth: Ceres does not count because it is in the asteroid belt. NASA counts it, and the IAU said in 2008 that Ceres is a dwarf planet even though it is not a plutoid.
• Myth: the IAU said no more can exist. The opposite is true. The IAU says there may be more than a hundred.
• Myth: a candidate list is official. Brown's page is one astronomer's ranking, and the Planetary Society's is another. Both are useful, and neither one is the IAU list.

Frequently asked questions

How many dwarf planets does NASA list?

Five: Ceres, Pluto, Haumea, Makemake and Eris. NASA's page was last updated on October 26, 2026.

Is Sedna a dwarf planet?

Not officially. Brown's list, dated November 10, 2026, places Sedna among the nearly certain candidates, with an estimated width of about 995 km (618 miles).

Why is Ceres on the list if it lives in the asteroid belt?

Ceres orbits the Sun, is nearly round and has not cleared its orbit, so it meets the dwarf planet definition. NASA describes it as the only dwarf planet in the inner Solar System.

Could the IAU add a sixth dwarf planet?

It could. The IAU says there may be many more, perhaps more than a hundred, but NASA's page gives no timetable for adding another.