In visible light, Ixion appears dark and moderately red in color due to organic compounds covering its surface.

Water ice has been suspected to be present on Ixion's surface, but may exist in trace amounts hidden underneath a thick layer of organic compounds.

[22][21] On the night of 22 May 2001, American astronomers James Elliot and Lawrence Wasserman identified Ixion in digital images of the southern sky taken with the 4-meter Víctor M. Blanco Telescope at Cerro Tololo.

[c] At the time of discovery, Ixion was thought to be among the largest trans-Neptunian objects in the Solar System, as implied by its high intrinsic brightness.

Zeus found out about his intentions and created the cloud Nephele in the shape of Hera, and tricked Ixion into coupling with it, fathering the race of Centaurs.

[34] For his crimes, Ixion was expelled from Olympus, blasted with a thunderbolt, and bound to a burning solar wheel in the underworld for all eternity.

Denis Moskowitz, a software engineer in Massachusetts who designed the symbols for most of the dwarf planets, substitutes the Greek letter iota (Ι) and xi (Ξ) for I and X, creating a variant ().

[2] Simulations by the Deep Ecliptic Survey show that Ixion can acquire a perihelion distance (qmin) as small as 27.5 AU over the next 10 million years.

[4] The rotation period of Ixion is uncertain; various photometric measurements suggest that it displays very little variation in brightness, with a small light curve amplitude of less than 0.15 magnitudes.

[10][11][40] Initial attempts to determine Ixion's rotation period were conducted by astronomer Ortiz and colleagues in 2001 but yielded inconclusive results.

[53][21][29] Under the assumption of a low albedo, it was presumed to have a diameter around 1,200 km (750 mi), which would have made it larger than the dwarf planet Ceres and comparable in size to Charon.

[48] Ixion's diameter was later revised to 617 km (383 mi), based on multi-band thermal observations by the Herschel Space Observatory along with Spitzer in 2013.

[8] Observers from the Lowell Observatory provided highly precise measurements of the occultation chord timing, allowing for tight constraints to Ixion's diameter and possible atmosphere.

The precise Lowell Observatory chords place an upper limit surface pressure of <2 microbars for any possible atmosphere of Ixion.

[9] Astronomer Gonzalo Tancredi considers Ixion as a likely candidate as it has a diameter greater than 450 km (280 mi), the estimated minimum size for an object to achieve hydrostatic equilibrium, under the assumption of a predominantly icy composition.

[12] In the visible spectrum, Ixion appears moderately red in color, similar to the large Kuiper belt object Quaoar.

[58] In the near-infrared, Ixion's reflectance spectrum appears neutral in color and lacks apparent absorption signatures of water ice at wavelengths of 1.5 and 2 μm.

[59] Ixion's featureless near-infrared spectrum indicates that its surface is covered with a thick layer of dark organic compounds irradiated by solar radiation and cosmic rays.

[60] In 2003, VLT observations tentatively resolved a weak absorption feature at 0.8 μm in Ixion's spectrum, which could possibly be attributed to surface materials aqueously altered by water.

Boehnhardt and colleagues suggested a mixing ratio of 6:1 for dark and bright material as a best-fit model for a geometric albedo of 0.08.

[61] The New Horizons spacecraft, which successfully flew by Pluto in 2015, observed Ixion from afar using its long range imager on 13 and 14 July 2016.

[12] In a study published by Ashley Gleaves and colleagues in 2012, Ixion was considered as a potential target for an orbiter mission concept, which would be launched on an Atlas V 551 or Delta IV HLV rocket.

For an orbiter mission to Ixion, the spacecraft have a launch date in November 2039 and use a gravity assist from Jupiter, taking 20 to 25 years to arrive.