Haumea
What is Haumea?
Dwarf planets· Diameter ~1,600 km (long axis 2,100 km). A dwarf planet stretched into a rugby-ball shape by its fast 3.9-hour spin. It has two moons and a thin ring.
Orbit and size
| Size | ~2,100 × 1,680 × 1,070 km |
|---|---|
| Distance | 35~51 AU |
| Year | 284 yr |
| Rotation | 3.9 h — fastest large body |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
The Haumea family, scattered by one collision
About a dozen small bodies travel on orbits similar to Haumea's. Their surfaces are coated with the same water ice, and their colours and brightness match. Scientists therefore think they are all fragments knocked off by a single great collision. Such a group is called a collisional family, and this was the first one identified beyond Neptune.
The same collision is thought to have produced Haumea's two moons. The larger, Hiʻiaka, is about 310 km across and orbits in 49 days; the smaller, Namaka, is about 150 km across and orbits in 18 days. Both are named after daughters of Haumea in Hawaiian myth. The collision probably happened early in the solar system's history, when the Kuiper belt was far more crowded than today.
On 21 January 2017 Haumea passed in front of a faint star, and telescopes at several sites in Europe timed how long the starlight vanished. The starlight also dimmed briefly before and after Haumea itself went by. The cause was a ring about 70 km wide, circling at a radius of about 2,290 km. It was the first ring ever found around a body beyond Neptune.
The dwarf planet in depth
Haumea is a dwarf planet in the Kuiper belt beyond Neptune. It swings between 35 and 51 AU from the Sun and takes 284 years to go around once, on an orbit tilted 28 degrees from the plane of the planets. It is named after the Hawaiian goddess of childbirth, and its mass is about a third of Pluto's.
Haumea's most striking feature is its fast spin. It turns once every 3.9 hours, so its day is less than a sixth as long as Earth's. Spinning this fast pushes the equator outward, and Haumea has been stretched into a rugby-ball shape about 2,100 km along its longest axis and about 1,070 km along its shortest. No other known body of this size spins so fast.
Scientists think Haumea suffered a huge collision long ago and that the impact set it spinning so quickly. Its surface is coated in glittering water ice, which makes it very bright, and one side has a dark red patch. In the orbit view you can see Haumea on a steeply tilted orbit at about Pluto's distance.
Frequently asked
- How far is Haumea from Earth?
- The distance of Haumea is 35~51 AU.
- How long is a day on Haumea?
- The rotation of Haumea is 3.9 h — fastest large body.
- In one line, what is Haumea?
- Dwarf planets — A dwarf planet stretched into a rugby-ball shape by its fast 3.9-hour spin.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.