Haumea
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, and formally announced in 2005 by a team headed by José Luis Ortiz Moreno at the Sierra Nevada Observatory in Spain, who had discovered it that year in precovery images taken by the team in 2003. From that announcement, it received the provisional designation.
On 17 September 2008, it was named after Haumea, the Hawaiian goddess of childbirth and fertility, under the expectation by the International Astronomical Union that it would prove to be a dwarf planet. Nominal estimates make it the third-largest known trans-Neptunian object, after Eris and Pluto, and approximately the size of Uranus's moon Titania. Precovery images of Haumea have been identified back to 22 March 1955.
Haumea's 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 are consistent with it being a Jacobi ellipsoid, with its major axis twice as long as its minor. In October 2017, astronomers announced the discovery of a ring system around Haumea, representing the first [|ring] system discovered for a trans-Neptunian object and a dwarf planet.
Haumea's gravity was until recently thought to be sufficient for it to have relaxed into hydrostatic equilibrium, though that is now unclear. Haumea's elongated shape, together with its rapid rotation, rings, and high albedo, is 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 and Haumea's two known moons, Hiiaka and Namaka.
History
Discovery
Two teams claim credit for the discovery of Haumea. A team consisting of Mike Brown of Caltech, David Rabinowitz of Yale University, and Chad Trujillo of Gemini Observatory in Hawaii discovered Haumea on 28 December 2004, on images they had taken on 6 May 2004. On 20 July 2005, they published an online abstract of a report intended to announce the discovery at a conference in September 2005.At around this time, José Luis Ortiz Moreno and his team at the Instituto de Astrofísica de Andalucía at Sierra Nevada Observatory in Spain found Haumea on images taken on 7–10 March 2003. Ortiz emailed the Minor Planet Center with their discovery on the night of 27 July 2005.
Brown initially conceded discovery credit to Ortiz, but came to suspect the Spanish team of fraud upon learning that the Spanish observatory had accessed Brown's observation logs the day before the discovery announcement, a fact that they did not disclose in the announcement as would be customary. Those logs included enough information to allow the Ortiz team to precover Haumea in their 2003 images, and they were accessed again just before Ortiz scheduled telescope time to obtain confirmation images for a second announcement to the MPC on 29 July. Ortiz later admitted he had accessed the Caltech observation logs but denied any wrongdoing, stating he was merely verifying whether they had discovered a new object.
IAU protocol is that discovery credit for a minor planet goes to whoever first submits a report to the MPC with enough positional data for a decent determination of its orbit, and that the credited discoverer has priority in choosing a name. However, the IAU announcement on 17 September 2008, that Haumea had been named by a dual committee established for bodies expected to be dwarf planets, did not mention a discoverer. The location of discovery was listed as the Sierra Nevada Observatory of the Spanish team, but the chosen name, Haumea, was the Caltech proposal. Ortiz's team had proposed "Ataecina", the ancient Iberian goddess of spring; as a chthonic deity, it would have been appropriate for a plutino, which Haumea was not.
Name and symbol
Until it was given a permanent name, the Caltech discovery team used the nickname "Santa" among themselves, because they had discovered Haumea on 28 December 2004, just after Christmas. The Spanish team were the first to file a claim for discovery to the Minor Planet Center, in July 2005. On 29 July 2005, Haumea was given the provisional designation 2003 EL61, based on the date of the Spanish discovery image. On 7 September 2006, it was numbered and admitted into the official minor planet catalog as 2003 EL61.Following guidelines established at the time by the IAU that classical Kuiper belt objects be given names of mythological beings associated with creation, in September 2006 the Caltech team submitted formal names from Hawaiian mythology to the IAU for both 2003 EL61 and its moons, in order "to pay homage to the place where the satellites were discovered". The names were proposed by David Rabinowitz of the Caltech team. Haumea is the matron goddess of the island of Hawaii, where Gemini and W. M. Keck Observatory are located on Mauna Kea. In addition, she is identified with Papa, the goddess of the earth and wife of Wākea, which, at the time, seemed appropriate because Haumea was thought to be composed almost entirely of solid rock, without the thick ice mantle over a small rocky core typical of other known Kuiper belt objects. Lastly, Haumea is the goddess of fertility and childbirth, with many children who sprang from different parts of her body; this corresponds to the swarm of icy bodies thought to have broken off the main body during an ancient collision. The two known moons, also believed to have formed in this manner, are thus named after two of Haumea's daughters, Hiiaka and Nāmaka.
The proposal by the Ortiz team, Ataecina, did not meet IAU naming requirements, because the names of chthonic deities were reserved for stably resonant trans-Neptunian objects such as plutinos that resonate 3:2 with Neptune, whereas Haumea was in an intermittent 7:12 resonance and so by some definitions was not a resonant body. The naming criteria would be clarified in late 2019, when the IAU decided that chthonic figures were to be used specifically for plutinos.
A planetary symbol for Haumea,, is included in Unicode at U+1F77B. Planetary symbols are no longer much used in astronomy, and ? is mostly used by astrologers, but has also been used by NASA. The symbol was designed by Denis Moskowitz, a software engineer in Massachusetts; it combines and simplifies Hawaiian petroglyphs meaning 'woman' and 'childbirth'.
Orbit
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 is currently more than 50 AU from the Sun. It will come to perihelion in 2133. 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, 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's future orbit is unlikely to be stable over the course of the Solar System. A study which simulated the future orbits of 34 trans-Neptunian objects showed Haumea was the most statistically likely to be ejected out of its orbit into outer space or the inner Solar System over the next billion years.
Possible resonance with Neptune
Haumea is thought to be in an intermittent 7:12 orbital resonance with Neptune. Its ascending node Ω precesses with a period of about 4.6 million years, and the resonance is broken twice per precession cycle, or every 2.3 million years, only to return a hundred thousand years or so later. As this is not a stable resonance, Marc Buie qualifies it as non-resonant.Rotation
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. While most rotating bodies in equilibrium are flattened into oblate spheroids, Haumea rotates so quickly that it is distorted into a triaxial ellipsoid. If Haumea were to rotate much more rapidly, it would distort itself into a dumbbell shape and split in two. This rapid rotation is thought to have been caused by the impact that created its satellites and collisional family.The plane of Haumea's equator is oriented nearly edge-on from Earth at present and is also slightly offset to the orbital planes of its ring and its outermost moon Hiiaka. Although initially assumed to be coplanar to Hiiaka's orbital plane by Ragozzine and Brown in 2009, their models of the collisional formation of Haumea's satellites consistently suggested Haumea's equatorial plane to be at least aligned with Hiiaka's orbital plane by approximately 1°. This was supported with observations of a stellar occultation by Haumea in 2017, which revealed the presence of a ring approximately coincident with the plane of Hiiaka's orbit and Haumea's equator. A mathematical analysis of the occultation data by Kondratyev and Kornoukhov in 2018 placed constraints on the relative inclination angles of Haumea's equator to the orbital planes of its ring and Hiiaka, which were found to be inclined and relative to Haumea's equator, respectively.