Dwarf Planet Haumea and the Outer Solar System

Theres an odd little world in the outer solar system called 136108 Haumea, or Haumea (for short). It orbits the Sun as part of the Kuiper Belt, far beyond the orbit of Neptune and in the same general region as Pluto. Planet searchers have been observing that region for years now, looking for other worlds. It turns out there are many of them out there, but none have been found — yet — as weird as Haumea. Its less like a sedately orbiting planet and more like a wildly spinning top. It lopes around the Sun once every 285 years, whirling madly, end over end. That motion tells planetary scientists that Haumea was sent into that propeller-like orbit by a collision with another body sometime in the past. Stats For a tiny world out in the middle of nowhere, Haumea presents some striking statistics. Its not very big and its shape is oblong, like a fat cigar that is 1920 kilometers long, about 1,500 km wide and 990 kilometers thick. It spins on its axis once every four hours. Its mass is about a third of Plutos, and planetary scientists classify it as a dwarf planet — similar to Pluto. Its more properly listed as a plutoid due to its ice-rock composition and its position in the solar system in the same region as Pluto. It has been observed for decades, although not recognized as a world until its official discovery in 2004 and the announcement in 2005. Mike Brown, of CalTech, was set to announce his teams discovery when they were beaten to the punch by a Spanish team who claimed to have seen it first. However, the Spanish team apparently accessed Browns observing logs just before Brown was set to make his announcement, and they claim to have discovered Haumea first.   The IAU credited the observatory in Spain for the discovery, but not the Spanish team. Brown was given the right to name Haumea and its moons (which is team discovered later).   Collision Family   The fast spinning motion that flips Haumea around as it orbits the Sun is the result of a long-ago collision between at least two objects. Its actually a member of whats called a collisional family which contains objects all created in an impact that took place very early in the solar systems history. The impact shattered the colliding objects and might also have removed much of primordial Haumeas ice, leaving it a largely rocky body with a thin layer of ice. Some measurements indicate that theres water ice on the surface. It appears to be fresh ice, meaning it was deposited within the past 100 million years or so. Ices in the outer solar system are darkened by ultraviolet bombardment, so fresh ice on Haumea implies some kind of activity. However, no one is sure what that would be. More studies are needed to understand this spinning world and its bright surface. Moons and Possible Rings Small as Haumea is, its large enough to have moons (satellites that orbit around it). Astronomers spotted two of them, called 136108 Haumea I Hiiaka and 136108 Hamuea II Namaka. They were found in 2005 by Mike Brown and his team using the Keck Observatory on Maunakea in Hawaii. Hiiaka is the outermost of the two moons and is only 310 kilometers across. It appears to have an icy surface and it might be a fragment of the original Haumea. The other moon, Namaka, orbits closer to Haumea. Its only about 170 kilometers across. Hiiaka orbits Haumea in 49 days, while Namaka takes only 18 days to go once around its parent body. In addition to the small moons, Haumea is thought to have at least one ring surrounding it. No observations have conclusively confirmed this, but eventually astronomers should be able to detect traces of it.   Etymology Astronomer who discover objects get the pleasure of naming them, according to guidelines set up by the International Astronomical Union. In the case of these distant worlds, the IAUs rules suggest that objects in the Kuiper Belt and beyond should be named after mythological beings associated with creation. So, the Brown team went to Hawaiian mythology and selected Haumea, who is the goddess of the island of Hawaii (from where the object was discovered using the Keck telescope). The moons are named after Haumeas daughters. Further Exploration   Its not too likely that a spacecraft would be sent to Haumea in the near future, so planetary scientists will continue to study it using ground-based telescopes and space-based observatories such as Hubble Space Telescope. There have been some preliminary studies aimed at developing a mission to this distant world. It would take a mission nearly 15 years to arrive there. One idea is to have it settle into orbit around Haumea and send back high-resolution images and data. So far, there are no concrete plans for a Haumea mission, although it would certainly be an interesting world to study up-close!