The outer Solar System dwarf planet Haumea has two known moons, Hiʻiaka and Namaka, named after Hawaiian goddesses. These small moons were discovered in 2005, from observations of Haumea made at the telescopes of the W. M. Keck Observatory in Hawaii. Haumeas moons are unusual in a number of ways and they are thought to be part of its extended collisional family, which formed billions of years ago from icy debris after a large impact disrupted Haumeas ice mantle. Hiʻiaka, the larger, outermost moon, has large amounts of water ice on its surface. Namaka, about one tenth the mass, has an orbit with surprising dynamics, it is unusually eccentric, two small satellites were discovered around Haumea through observations using the W. M. Keck Observatory by a Caltech team in 2005. The outer and larger of the two satellites was discovered January 26,2005, and formally designated S/20051, though nicknamed Rudolph by the Caltech team. The smaller, inner satellite of Haumea was discovered on June 30,2005, formally termed S/20052, on September 7,2006, both satellites were numbered and admitted into the official minor planet catalogue as 2003 EL61 I and II, respectively. The permanent names of these moons were announced, together with that of 2003 EL61, by the International Astronomical Union on September 17,2008, Haumea I Hiʻiaka, each moon was named after a daughter of Haumea, the Hawaiian goddess of fertility and childbirth. Hiʻiaka is the goddess of dance and patroness of the Big Island of Hawaii, Nāmaka is the goddess of water and the sea, she cooled her sister Peles lava as it flowed into the sea, turning it into new land. In her legend, Haumeas many children came from different parts of her body, there could therefore be additional outer moons, smaller than Namaka, that have not yet been detected. This makes it unlikely that any more exist, Hiʻiaka is the outer and, at roughly 350 km in diameter, the larger and brighter of the two moons. Strong absorption features observed at 1.5,1.65 and 2 µm in its infrared spectrum are consistent with nearly pure crystalline water ice covering much of its surface. The sizes of both moons are calculated with the assumption that they have the same infrared albedo as Haumea, Haumeas albedo has been measured by the Spitzer Space Telescope, from ground-based telescopes, the moons are too small and close to Haumea to be seen independently. Based on this common albedo, the moon, Namaka. The Hubble Space Telescope has adequate angular resolution to separate the light from the moons from that of Haumea, Hiʻiaka orbits Haumea nearly circularly every 49 days. Namaka orbits Haumea in 18 days in an elliptical, non-Keplerian orbit, and as of 2008 was inclined 13° with respect to Hiʻiaka. Namakas orbit has likely been disturbed by resonances with the more-massive Hiʻiaka due to converging orbits as they moved outward from Haumea due to tidal dissipation. They may have caught in and then escaped from orbital resonance several times
Keck image of Haumea and its moons. Hiʻiaka is above Haumea (center), and Namaka is directly below.
Scale diagram of Haumea, the ring, and orbits of its two moons
A view of the orbits of Hiʻiaka (blue) and Namaka (green)