Hugo's Solar System
Dwarf planet
Haumea
The egg-shaped dwarf planet that spins so fast a day lasts four hours
Haumea is oval and spins with great speed.
Her surface is shiny and icy indeed.From Hugo's Journey Through Space
Key facts
- Diameter
- About 1,080 miles / 1,740 km at the equator (mean about 1,550 km); shaped like a rugby ball
- Distance from the Sun
- About 43 AU (about 4,010 million miles / 6,450 million km) on average
- One orbit
- About 285 Earth years
- One day (rotation)
- About 3.9 hours, the fastest of any large body in the solar system
- Average temperature
- Below about -220 °C
- Known moons
- 2 (as of September 2026)
- Rings
- One thin ring about 43.5 miles / 70 km wide, found in 2017
- Named after
- Haumea, the Hawaiian goddess of fertility and childbirth
- Discovered
- In images from 2003 and 2004; disputed between a Spanish team and a Caltech team, named in 2008
- Visited by
- No spacecraft yet; studied only by telescopes
About Haumea
Haumea is a dwarf planet. It lives far, far from the Sun. It is very cold there. Haumea is not round like a ball. It looks like a squashed egg. That is because it spins so fast. One day on Haumea lasts four hours. It is made of rock and ice. It has two small moons. Haumea has a thin ring too. It is named after a goddess. She comes from the islands of Hawaii. Hugo thinks it is a very odd world.
Haumea is a dwarf planet that lives in the Kuiper Belt, far beyond Neptune. It is about 43 times farther from the Sun than Earth is. Sunlight takes around 6 hours to reach it, so Haumea is dark and cold. One orbit of the Sun takes Haumea about 285 Earth years.
Most large worlds are shaped like a sphere, but Haumea is not. It rotates once every 4 hours, faster than any other large body we know. Spinning that fast stretches Haumea into a shape like a rugby ball. NASA gives its diameter as about 1,740 kilometres, roughly a seventh of Earth's width.
Astronomers think Haumea is mostly rock covered with a shiny coat of ice. Its gravity holds on to two small moons, named Hi'iaka and Namaka. Both moons were discovered in 2005 using large telescopes on Earth. In 2017, astronomers watched Haumea pass in front of a distant star.
The starlight dimmed twice, which revealed a thin ring around the dwarf planet. Haumea was the first object in the Kuiper Belt known to have a ring. Haumea is named after the Hawaiian goddess of fertility and childbirth. Her two daughters gave their names to the moons.
No spacecraft has ever visited Haumea, so everything we know comes from telescopes.
Haumea is a dwarf planet in the Kuiper Belt. It orbits the Sun at an average distance of about 43 AU (roughly 6.5 billion km), on a path that carries it from about 34.7 AU to 51.4 AU, tilted 28 degrees to the plane of the planets. One orbit takes about 283 to 285 years, and sunlight takes around six hours to reach it. The surface is below about 50 K (roughly minus 220 degrees Celsius).
Its defining feature is its spin. Haumea rotates once every 3.9 hours, the fastest known rotation of any large body in the solar system. That spin has drawn it into an elongated ellipsoid rather than a sphere: occultation measurements give axes of roughly 2,100 by 1,700 by 1,000 km. NASA quotes an equatorial diameter of about 1,740 km, but any single diameter is approximate for so lopsided an object; the mean diameter is closer to 1,550 km, which makes Haumea the third-largest known trans-Neptunian object after Pluto and Eris. Its mass is about 4 x 10^21 kg, and its density of about 2 g/cm3 points to a rocky interior beneath a thin, highly reflective coating of crystalline water ice.
Haumea has two known moons as of August 2026, both discovered in 2005 by Michael Brown's team at the Keck Observatory. Hi'iaka, the outer and larger moon, is a few hundred kilometres across and orbits in about 49 days; Namaka, about 150 km across, orbits in about 18 days. Haumea also heads a collisional family of icy bodies on similar orbits, probably debris from an ancient impact that may also explain its rapid spin. On 21 January 2017, a stellar occultation revealed a ring about 2,290 km from Haumea's centre and about 70 km wide, the first ring found around a Kuiper Belt object.
The discovery is disputed. Brown's team identified Haumea on 28 December 2004 in images taken on 6 May 2004; a team at the Sierra Nevada Observatory in Spain, led by Jose Luis Ortiz, announced it first in 2005 from images taken on 7 March 2003. When the International Astronomical Union adopted the name Haumea, the Hawaiian goddess of fertility, on 17 September 2008, it credited neither team; the moons are named after her daughters. No spacecraft has visited Haumea; everything known about it comes from telescopes and occultation campaigns.
Did you know?
- Haumea spins so fast that it has been stretched into an egg shape about twice as long as it is thick.
- Haumea's ring was found in 2017 when the dwarf planet passed in front of a distant star and the starlight dimmed twice.
- Two teams claimed to have discovered Haumea, so when it was named in 2008 nobody was officially listed as the discoverer.
Moons of Haumea
Haumea has 2 known moons as of September 2026. The largest are listed here. How many moons does Haumea have?
Questions children ask
Why is Haumea shaped like an egg?
Haumea rotates once every 4 hours, faster than any other large body we know of. Spinning that fast flings its middle outwards, so instead of settling into a sphere it has stretched into a long, flattened shape like a rugby ball.
Does Haumea have moons?
Yes. As of August 2026 it has two known moons, Hi'iaka and Namaka, both found in 2005. They are named after the daughters of the Hawaiian goddess Haumea. Hi'iaka is the larger one and takes about 49 days to orbit.
Has a spacecraft been to Haumea?
No. Haumea is about 43 times farther from the Sun than Earth, and no mission has flown there. Everything we know comes from telescopes on Earth and from watching Haumea pass in front of distant stars.
How long is a year on Haumea?
One trip around the Sun takes Haumea about 285 Earth years. It has not completed even one full orbit since astronomers first spotted it in 2003, and it will not do so for centuries.
Quick quiz
Three questions for space cadets. Nothing is recorded.
- How long does one day on Haumea last?
- What shape is Haumea?
- How many known moons does Haumea have, as of August 2026?
Pluto
Makemake
Eris