Haumea

Haumea (minor-planet designation 136108 Haumea) is a dwarf planet located beyond Neptune's orbit. It was discovered in 2004 by a team headed by Mike Brown of Caltech at the Palomar Observatory, and formally announced in 2005 by a team headed by José Luis Ortiz Moreno at the Sierra Nevada Observatory in Spain, who had discovered it that year in precovery images taken by the team in 2003. From that announcement, it received the provisional designation 2003 EL61. On September 17, 2008, it was named after Haumea, the Hawaiian goddess of childbirth, under the expectation by the International Astronomical Union (IAU) that it would prove to be a dwarf planet. Nominal estimates make it the third-largest known trans-Neptunian object, after Eris and Pluto, and approximately the size of Uranus's moon Titania. Precovery images of Haumea have been identified back to March 22, 1955.

136108 Haumea
Low-resolution Hubble Space Telescope image of Haumea and its two moons, Hi'iaka (top) and Namaka (bottom), June 2015
Discovery
Discovered by
Discovery date
  • March 7, 2003 (Ortiz)
  • December 28, 2004 (Brown)
Designations
MPC designation
(136108) Haumea
Pronunciation/hˈm.ə, ˌhɑː-/
Named after
Haumea
Alternative designations
2003 EL61
Minor planet category
AdjectivesHaumean
Symbol (mostly astrological)
Orbital characteristics
Epoch December 17, 2020 (JD 2459200.5)
Uncertainty parameter 2
Observation arc65 years and 291 days (24033 days)
Earliest precovery dateMarch 22, 1955
Aphelion51.585 AU (7.7170 Tm)
Perihelion34.647 AU (5.1831 Tm)
Semi-major axis
43.116 AU (6.4501 Tm)
Eccentricity0.19642
Orbital period (sidereal)
283.12 yr (103,410 days)
Average orbital speed
4.53 km/s
Mean anomaly
218.205°
Mean motion
0° 0m 12.533s / day
Inclination28.2137°
Longitude of ascending node
122.167°
≈ June 1, 2133
±2 days
239.041°
Known satellites2 (Hiʻiaka and Namaka)
Physical characteristics
Dimensions
  • ≈ 2,100×1,680×1,074km
  • 2,322±60×1,704±8×1,026±32km
Mean radius
  • 780 km
  • 798±6 km to 816 km
Surface area
8.14×106 km2
Volume1.98×109 km3
0.0018 Earths
Mass(4.006±0.040)×1021 kg
0.00066 Earths
Mean density
  • 2.018 g/cm3
  • 1.885±0.080 g/cm3 to 1.757 g/cm3
Equatorial surface gravity
0.93 m/s2 at poles
to 0.24 m/s2 at longest axis
Equatorial escape velocity
1 km/s at poles
to 0.71 km/s at longest axis
Sidereal rotation period
3.915341±0.000005 h
(0.163139208 d)
≈ 126° (to orbit; assumed)
81.2° or 78.9° (to ecliptic)
North pole right ascension
282.6°±1.2°:3174
North pole declination
−13.0°±1.3° or −11.8°±1.2°:3174
Temperature<50 K
  • BB (neutral)
  • B−V = 0.64, V−R = 0.33
  • B0−V0 = 0.646
17.3 (opposition)
0.428±0.011 (V-band) · 0.2

Haumea's mass is about one-third that of Pluto, and 1/1400 that of Earth. Although its shape has not been directly observed, calculations from its light curve are consistent with it being a Jacobi ellipsoid (the shape it would be if it were a dwarf planet), with its major axis twice as long as its minor. In October 2017, astronomers announced the discovery of a ring system around Haumea, representing the first ring system discovered for a trans-Neptunian object and a dwarf planet. Haumea's gravity was until recently thought to be sufficient for it to have relaxed into hydrostatic equilibrium, though that is now unclear. Haumea's elongated shape together with its rapid rotation, rings, and high albedo (from a surface of crystalline water ice), are thought to be the consequences of a giant collision, which left Haumea the largest member of a collisional family that includes several large trans-Neptunian objects and Haumea's two known moons, Hiʻiaka and Namaka.

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