Hiʻiaka is the larger, outer moon of the dwarf planet Haumea.
Hiʻiaka is a large moon and the 22th largest moon in the Solar System currently known.
Hiʻiaka is too faint to detect with telescopes smaller than about 2 metres in aperture, though Haumea itself has a visual magnitude of 17.5, making it the third brightest object in the Kuiper belt after Pluto and Makemake, and easily observable with a large amateur telescope.
Discovery
Hiʻiaka is discovered on 26 Jan 2005 by the team of Michael E. Brown, Chadwick A. Trujillo, David Lincoln Rabinowitz, etc from observations of Haumea made at the large telescopes of the W. M. Keck Observatory in Hawaii.
Naming
Initially it had gone by the nickname "Rudolph" by its discovery team, as Haumea itself is nicknamed "Santa".
Rudolph the Red-Nosed Reindeer is a reindeer with a glowing red nose. He is popularly known as "Santa's 9th Reindeer" and, when depicted, is the lead reindeer pulling Santa's sleigh on Christmas Eve. The luminosity of his nose is so great that it illuminates the team's path through inclement winter weather.
It is later officially named after one of the daughters of Haumea. Hiʻiaka is the goddess of dance and patroness of the Big Island of Hawaii, where the Mauna Kea Observatory is located.
In Hawaiian mythology, Hiʻiaka is a daughter of Haumea and Kāne. She was the patron goddess of Hawaiʻi and the hula dancers, and takes on the task of bearing the clouds - variously, those of storms and those produced by her sister's volcanos, and lived in a grove of Lehua trees which are sacred to her where she spent her days dancing with the forest spirits. She is also called Hiʻiaka-i-ka-poli-o-Pele literally meaning "Cloud bearer cradled in the bosom of Pele". Hiʻiaka was conceived in Tahiti, but carried in the form of an egg to Hawaiʻi by Pele, who kept the egg with her at all times to incubate it. Hiʻiaka is Pele's favorite and most loyal sister.
Stats
Diameter (estimated): 310 km
Semi-major axis: 49,880 km
Orbital Period: 49.12 days
Rotation Period: ?
Formation
Haumea's moons are unusual in a number of ways. 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 Haumea's ice mantle.
The dwarf planet Haumea appears to be almost entirely made of rock, with only a superficial layer of ice; most of the original icy mantle is thought to have been blasted off by the impact that spun Haumea into its current high speed of rotation, where the material formed into the small Kuiper belt objects in Haumea's collisional family and the two known Haumea moons.
Surface properties
Hiʻiaka, the larger, outermost moon, has large amounts of pure water ice on its surface, a feature rare among Kuiper belt objects.
Strong absorption features observed at 1.5, 1.65 and 2 micrometres in its infrared spectrum are consistent with nearly pure crystalline water ice covering much of its surface. The unusual spectrum, and its similarity to absorption lines in the spectrum of Haumea, led Brown and colleagues to conclude that it was unlikely that the system of moons was formed by the gravitational capture of passing Kuiper belt objects into orbit around the dwarf planet. Instead, the Haumean moons must be fragments of Haumea's ice mantle.
How big is it?
The size of Hi'iaka is calculated with the assumption that it has the same infrared albedo as Haumea, which is reasonable as the spectra show them to have the same surface composition. Haumea's albedo has been measured by the Spitzer Space Telescope and from ground-based telescopes, while Hi'iaka is too small and close to Haumea to be seen independently. Based on this common albedo, Hiʻiaka is estimated to be about 310 km in diameter.
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