(28978) Ixion

(28978) Ixion (provisionally designated 2001 KX₇₆) is a Kuiper belt object, more specifically, a plutino. It was discovered on May 22, 2001 by the Deep Ecliptic Survey, and is named after Ixion, a figure from Greek mythology.

Like Pluto, it is not considered a planet, but unlike this Ixion is a dwarf planet candidate.

Physical characteristics

Ixion is moderately red (slightly more than (50000) Quaoar) and has a higher albedo than medium red cubewans.

The latest spectroscopic results indicate that the surface of Ixion is a mixture of dark carbon and a heteropolymer formed by irradiation of clathrates of water and organic compounds, known as Tolina (from English tholin (see spectra of trans-Neptunian objects). The water ice absorption lines (1.5 and 2μm) are not found. Unlike what happens in (20000) Varuna, Ixion does not show a special reflectivity for long waves (the so-called spectral inclination) with infrared.

Orbit

This diagram shows the orbits of Ixion (green), Pluto (red) and Neptune (gris). The positions indicated are those for April 2006.

Ixion and Pluto follow similar orbits but are oriented differently: Ixion's perihelion is below the ecliptic, while Pluto's is above it. Unlike what normally happens with bodies in resonance with Neptune, Ixion approaches Pluto with less than 20 degrees of angular separation. Ixion is currently crossing the ecliptic downward, and will reach perihelion in 2070. Pluto passed perihelion in 1989 and is descending toward the ecliptic.