Haumea (dwarf Planet) - Orbit and Rotation

Orbit and Rotation

Haumea has a typical orbit for a classical Kuiper-belt object, with an orbital period of 283 Earth years, a perihelion of 35 AU, and an orbital inclination of 28°. It passed aphelion in early 1992, and is currently more than 50 AU from the Sun.

Haumea's orbit has a slightly greater eccentricity than the other members of its collisional family. This is thought to be due to Haumea's weak fifth-order 12:7 orbital resonance with Neptune gradually modifying its initial orbit over the course of a billion years, through the Kozai effect, which allows the exchange of an orbit's inclination for increased eccentricity.

With a visual magnitude of 17.3, Haumea is the third-brightest object in the Kuiper belt after Pluto and Makemake, and easily observable with a large amateur telescope. However, since the planets and most small Solar System bodies share a common orbital alignment from their formation in the primordial disk of the Solar System, most early surveys for distant objects focused on the projection on the sky of this common plane, called the ecliptic. As the region of sky close to the ecliptic became well explored, later sky surveys began looking for objects that had been dynamically excited into orbits with higher inclinations, as well as more distant objects, with slower mean motions across the sky. These surveys eventually covered the location of Haumea, with its high orbital inclination and current position far from the ecliptic.

Haumea displays large fluctuations in brightness over a period of 3.9 hours, which can only be explained by a rotational period of this length. This is faster than any other known equilibrium body in the Solar System, and indeed faster than any other known body larger than 100 km in diameter. This rapid rotation is thought to have been caused by the impact that created its satellites and collisional family.