Haumea (dwarf Planet) - Moons

Moons

Two small satellites have been discovered orbiting Haumea, (136108) Haumea I Hiʻiaka and (136108) Haumea II Namaka. Brown's team discovered both in 2005, through observations of Haumea using the W.M. Keck Observatory.

Hiʻiaka, at first nicknamed "Rudolph" by the Caltech team, was discovered January 26, 2005. It is the outer and, at roughly 310 km in diameter, the larger and brighter of the two, and orbits Haumea in a nearly circular path every 49 days. Strong absorption features at 1.5 and 2 micrometres in the infrared spectrum are consistent with nearly pure crystalline water ice covering much of the surface. The unusual spectrum, along with similar absorption lines on Haumea, led Brown and colleagues to conclude that capture was an unlikely model for the system's formation, and that the Haumean moons must be fragments of Haumea itself.

Namaka, the smaller, inner satellite of Haumea, was discovered on June 30, 2005, and nicknamed "Blitzen". It is a tenth the mass of Hiʻiaka, orbits Haumea in 18 days in a highly elliptical, non-Keplerian orbit, and as of 2008 is inclined 13° from the larger moon, which perturbs its orbit. The relatively large eccentricities together with the mutual inclination of the orbits of the satellites are unexpected as they should have been damped by the tidal effects. A relatively recent passage by a (3:1) resonance might explain the current excited orbits of the Haumean moons.

At present, the orbits of the Haumean moons appear almost exactly edge-on from Earth, with Namaka periodically occulting Haumea. Observation of such transits would provide precise information on the size and shape of Haumea and its moons, as happened in the late 1980s with Pluto and Charon. The tiny change in brightness of the system during these occultations will require at least a medium-aperture professional telescope for detection. Hiʻiaka last occulted Haumea in 1999, a few years before discovery, and will not do so again for some 130 years. However, in a situation unique among regular satellites, Namaka's orbit is being greatly torqued by Hiʻiaka, preserving the viewing angle of Namaka–Haumea transits for several more years.