136108 Haumea, is a dwarf planet located beyond Neptune's orbit. It was discovered in 2004
by a team headed by Mike Brown of Caltech at the Palomar Observatory in the United States
and independently 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 recognized as a dwarf planet by the International Astronomical
Union (IAU) and named after Haumea, the Hawaiian goddess of childbirth.
Its 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 indicate that it is a triaxial ellipsoid, with
its major axis twice as long as its minor. Its gravity is thought to be sufficient for it to have
relaxed into hydrostatic equilibrium, making it a dwarf planet.
Haumea's elongated shape together with its rapid rotation, high density, 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 (TNOs) and Haumea's two known moons, Hi’iaka and Namaka.
Haumea has an orbital period of 284 Earth years, a perihelion of 35 AU, and an orbital inclination
of 28°. It passed aphelion in early 1992 and at the date of this image was 50.6 AU from the Sun.
Haumea's orbit has a slightly greater eccentricity than that of the other members of its collisional
family. This is thought to be due to Haumea's weak 7:12 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, because 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.
This image comprises 5 x Luminance (180 seconds each) , 0.5m f/2.9 ASA Astrograph with FLI
ML3200 camera at an altitude of 75 degrees on 21 April 2017, 8 days after opposition at
magnitude 17.3. The bright star to the south-east is magnitude 8.5 SAO 100875 in Bootes.
The field of view is 18’ x 18’.
Hills Observatory: 1 January 2013 to 22 March 2020