Themisto is a small, irregular moon that orbits inside the Himalia prograde group (this group includes Leda, Himalia, Lysithea, Elara, and S/2000 J11) and outside the Galilean satellites, but does not belong to either group. The Galileans all orbit almost perfectly in Jupiter's equatorial plane and have almost circular orbits. The Himalias have orbital eccentricities between 0.1 and 0.25, and they all orbit at about 27 degrees to Jupiter's equatorial plane.Themisto, however, has an eccentricity of 0.248 and orbits at a very high angle of 43 degrees to the equatorial plane. Little is known about Themisto. It is likely to be a captured asteroid, perhaps in a degrading orbit preparing to crash into the planet.
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