Haumea
Haumea is a dwarf planet in the Kuiper belt spun into an egg shape by a ≈3.9-hour rotation, one of the fastest of any large body. It has two moons and a thin ring. No spacecraft has visited.
Key facts
Science
Physical
- Mass
- 4.01 × 10²¹ kg · 0.0546 Moon masses
- Mean radius
- 780 km · 12% of Earth's radius
- Density
- 2,015 kg/m³ · 2× water
- Computed from mass and radius
- Surface gravity
- 0.439 m/s² · 4% of Earth's gravity
- Computed from mass and radius
- Escape velocity
- 828 m/s · 7% of Earth's escape velocity
- Computed from mass and radius
Orbital
- Distance from the Sun
- 49.7 AU
- Computed from the position at the selected time
- Semi-major axis
- 43.1 AU
- Computed from the cached state vector
- Eccentricity
- 0.1938
- Computed from the cached state vector
- Inclination
- 24.83 °
- Computed from the cached state vector
- Orbital period
- 282.87 years
- Computed from the cached state vector
- Perihelion
- 34.7 AU
- Computed from the orbital elements
- Aphelion
- 51.4 AU
- Computed from the orbital elements
- Mean orbital velocity
- 4.54 km/s
- Computed from the orbital elements
Rotation
- Rotation period
- 3.92 hours
Composition
- Bulk composition
- A surface of nearly pure crystalline water ice over a predominantly rocky body, inferred from spectroscopy and its high density; the rapid spin stretches it into an ellipsoid.
- Surface imagery
- No real surface imagery exists — this object has never been visited; color is approximate, inferred from spectroscopy.
Radiation & temperature
- Insolation
- 0.000539 S⊕ · 1/1,857 of the sunlight Earth receives
- Computed from the distance to the Sun (inverse-square; Earth's sunlight = 1), before any atmosphere.
- Geometric albedo
- 0.66
- V-band geometric albedo; Bond albedo not directly measured.
- Equilibrium temperature
- 32 K (-241 °C)
- Computed from albedo + distance from the Sun (airless black body); uses the geometric albedo as an estimate
Discovery & history
- Discovered
- December 28, 2004
- By
- Teams led by Mike Brown (Caltech) and José Luis Ortiz (Spain), amid a priority dispute
- Method
- Photographic plates
- Name
- The Hawaiian goddess of fertility and childbirth; its moons are named for her daughters.
Haumea was first detected on 28 December 2004 by a team led by Mike Brown at Caltech — who codenamed it 'Santa' for its Christmas-time discovery — and independently reported in 2005 by José Luis Ortiz's group in Spain from 2003 images (provisional designation 2003 EL61), sparking a lasting priority dispute. It is one of the fastest-spinning large bodies known, whirling around every ~3.9 hours into an elongated, egg-like shape, and in 2017 a stellar occultation revealed a ring — the first found around a trans-Neptunian object. It was named for Haumea, the Hawaiian goddess of fertility and childbirth; its two moons, Hiʻiaka and Namaka, are named for her daughters.
Images
Images from open archives · credit shown per image