28978 Ixion ("ik SIGH un", sometimes "ICK see un") is a Kuiper belt object discovered on May 22, 2001 with a diameter of approximately 1055 km and a semimajor axis of about 39.5 AU. Ixion is a Plutino: it has a 3:2 orbital resonance with Neptune.

28978 Ixion

Orbital characteristics
Orbit type	Plutino
Semimajor axis	39.4851 AU
Eccentricity	0.2416
Orbital period	248 Years
Inclination	19.627°
Physical characteristics
Diameter	1055? km
Albedo	?
History
Discoverer	Deep Ecliptic Survey
Discovery Date	2001-05-22

Little is known about Ixion. The latest spectroscopy results indicate that it has a surface that is a mixture of dark carbon and tholin, which is a heteropolymer formed by irradiation of clathrates of water and organic compounds (such as methane or ethane).

28978 Ixion is named after Ixion, a figure from Greek mythology. It previously had the systematic name 2001 KX₇₆.

Reference

• Pre-print http://www.astro.helsinki.fi/~psr/Papers/Ixion-AAL.pdf about Ixion's surface from the Planetary Systems Research group of the University of Helsinki.