High Quality Content by WIKIPEDIA articles! 28978 Ixion is a Kuiper belt object discovered on May 22, 2001. Ixion is a plutino (an object that has a 2:3 orbital resonance with Neptune) and a very likely dwarf planet; its diameter of 650 km estimated by Spitzer makes it about the fifth largest plutino. It is named after Ixion, a figure from Greek mythology. Ixion was discovered by the Cerro Tololo Inter-American Observatory (807). It is a moderately red color in visible light and has a surface made of a mixture of tholin and water ice. Light-curve-amplitude analysis shows only small deviations, suggesting Ixion is a spheroid with small albedo spots and hence a dwarf planet.