Icy Remnants

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Science  24 Apr 2009:
Vol. 324, Issue 5926, pp. 441
DOI: 10.1126/science.324_441a

Like Pluto, the dwarf planet Haumea is one of the largest known Kuiper Belt objects that lie beyond the orbit of Neptune. It is thought to be the remnant of an even larger body, which fragmented as a result of a collision, leaving behind Haumea itself, its two moons, Hi'iaka and Namaka, and a cluster of smaller icy debris whose surface properties and orbits have been shown to match those of Haumea. Now Fraser and Brown have taken near-infrared images of Haumea and its two satellites (illustrated at right) with the Hubble Space Telescope. The data showed that, like Haumea, Hi'iaka and Namaka are peculiar Kuiper Belt objects in that they are covered in pure water ice, reinforcing the idea that they are fragments of the collision that formed the triple system. Had Haumea gravitationally captured its two satellites, their surfaces would not be expected to match that of the dwarf planet, because Kuiper Belt objects have a wide range of surface compositions.

Astrophys. J. 695, L1 (2009).

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