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, meaning it has a 3:2 orbital resonance with Neptune.
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 provisional designation 2001 KX76.
