28978 Ixion
28978 Ixion (/ɪkˈsaɪ.ən/, provisional designation 2001 KX76) is a large trans-Neptunian object and a possible dwarf planet. It is located in the Kuiper belt, a region of icy objects orbiting beyond Neptune in the outer Solar System. Ixion is classified as a plutino, a dynamical class of objects in a 2:3 orbital resonance with Neptune. It was discovered in May 2001 by astronomers of the Deep Ecliptic Survey at the Cerro Tololo Inter-American Observatory, and was announced in July 2001. The object is named after the Greek mythological figure Ixion, who was a king of the Lapiths.
Hubble Space Telescope image of Ixion taken in 2006 | |
| Discovery | |
|---|---|
| Discovered by | Deep Ecliptic Survey |
| Discovery site | Cerro Tololo Obs. |
| Discovery date | 22 May 2001 |
| Designations | |
MPC designation | (28978) Ixion |
| Pronunciation | /ɪkˈsaɪ.ən/ |
Named after | Ιξίων Ixīōn |
Alternative designations | 2001 KX76 |
Minor planet category | TNO · plutino · distant |
| Adjectives | Ixionian /ɪksiˈoʊniən/ |
| Symbol | or (astrological) |
| Orbital characteristics | |
| Epoch 17 December 2020 (JD 2459200.5) | |
| Uncertainty parameter 3 | |
| Observation arc | 35.93 yr (13,122 days) |
| Earliest precovery date | 17 July 1982 |
| Aphelion | 49.584 AU |
| Perihelion | 30.019 AU |
Semi-major axis | 39.802 AU |
| Eccentricity | 0.24579 |
Orbital period (sidereal) | 251.11 yr (91,717 d) |
Mean anomaly | 289.587° |
Mean motion | 0° 0m 14.13s / day |
| Inclination | 19.600° |
Longitude of ascending node | 71.011° |
| ≈ 24 September 2070 ±1 day | |
| 298.314° | |
| Physical characteristics | |
| Dimensions | 756.9 km × 684.9 km (projected, occultation) |
Mean diameter | 709.6±0.2 km |
Synodic rotation period | 12.4±0.3 h 15.9±0.5 h |
| 0.108±0.002 geometric 0.037±0.007 Bond | |
| Temperature | 64+0.7 −1.1 K |
| IR (moderately red) B–V=1.009±0.051 V–R=0.61±0.03 V–I=1.146±0.086 | |
| 19.8 | |
| 3.774±0.021 3.6 (assumed) | |
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. Ixion has a measured diameter of 710 km (440 mi), making it the fourth-largest known plutino. Several astronomers have considered Ixion to be a possible dwarf planet, whereas others consider it a transitional object between irregularly-shaped small Solar System bodies and spherical dwarf planets. Ixion is currently not known to have a natural satellite, so its mass and density remain unknown.