Haumea (minor-planet designation 136108 Haumea) is a dwarf planet located beyond Neptune's orbit.[25] It was discovered in 2004 by a team headed by Mike Brown of Caltech at the Palomar Observatory in the United States and disputably also in 2005 by a team headed by José Luis Ortiz Moreno at the Sierra Nevada Observatory in Spain, though the latter claim has been contested. 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.

136108 Haumea 🝻
Hubble image of Haumea (center) and its two moons; Hiʻiaka is above Haumea and Namaka is below
Discovered by
Discovery date
  • December 28, 2004 (Brown)
  • July 27, 2005 (Ortiz)
(136108) Haumea
Pronunciation/hˈm.ə, ˌhɑː-/[nb 1]
Named after
2003 EL61
Orbital characteristics[8]
Epoch 17 December 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)
43.116 AU (6.4501 Tm)
283.12 yr (103,410 days)[9]
4.53 km/s[nb 2]
0° 0m 12.533s / day
≈ 1 June 2133[10]
±2 days
Known satellites2 (Hiʻiaka and Namaka)
Physical characteristics
  • ≈ 2,100×1,680×1,074km[nb 3][11]
  • 2,322±60×1,704±8×1,026±32km[nb 4][12]
Mean radius
8.14×106 km2[nb 3][13]
Volume1.98×109 km3[nb 3][14]
0.0018 Earths
Mass(4.006±0.040)×1021 kg[15]
0.00066 Earths
Mean density
  • 2.018 g/cm3[nb 3]
  • 1.885±0.080 g/cm3 to 1.757 g/cm3[nb 5]
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
3.915341±0.000005 h[16]
(0.163139208 d)
≈ 126° (to orbit; assumed)
81.2° or 78.9° (to ecliptic)[nb 6]
North pole right ascension
North pole declination
−13.0°±1.3° or −11.8°±1.2°[17]:3174
Temperature<50 K[20]
17.3 (opposition)[23][24]
0.428±0.011 (V-band)[16] · 0.2[9]

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. 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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