| Discovery | |
|---|---|
| Discovered by | David C. Jewitt, Scott S. Sheppard and Jan Kleyna |
| Discovery date | 9 December 2001 |
| Designations | |
| (148975) 2001 XA255 | |
| Centaur | |
| Orbital characteristics[1] | |
| Epoch 13 January 2016 (JD 2457400.5) | |
| Uncertainty parameter 2 | |
| Observation arc | 3812 days (10.44 yr) |
| Aphelion | 48.731 AU (7.2901 Tm) |
| Perihelion | 9.3364 AU (1.39671 Tm) |
| 29.034 AU (4.3434 Tm) | |
| Eccentricity | 0.67843 |
| 156.44 yr (57141.1 d) | |
| 12.809° | |
| 0° 0m 22.681s / day | |
| Inclination | 12.628° |
| 105.89° | |
| 90.452° | |
| Jupiter MOID | 4.12722 AU (617.423 Gm) |
| Physical characteristics | |
Mean diameter | 12.5 km[2] 38 km[1][3] |
| 0.041[1][3] | |
| 11.1[1] | |
(148975) 2001 XA255, provisional designation: 2001 XA255, is a dark minor planet in the outer Solar System, classified as centaur, approximately 38 kilometers (24 miles) in diameter.[1] It was discovered on 9 December 2001, by David C. Jewitt, Scott S. Sheppard, and Jan Kleyna observing from the Mauna Kea Observatory.[4] The object is currently trapped in a 1:1 mean-motion resonance with Neptune following a path of the horseshoe type.[5]
2001 XA255 follows a very eccentric orbit (0.68) with perihelion just inside the orbit of Saturn, aphelion in the trans-Neptunian belt and a semi-major axis of 28.9 AU. The orbital inclination of this object is moderate at 12.6º.[1]
2001 XA255 was identified as trapped in a 1:1 mean-motion resonance with Neptune and 1:2 with Uranus by T. Gallardo in 2006.[6] The object is dynamically unstable and it entered the region of the giant planets relatively recently, perhaps 50,000 years ago, from the scattered disk. It follows a short-lived horseshoe orbit around Neptune.[5]
The object has an estimated diameter of 12.5 km and it was classified as an inactive centaur by David Jewitt.[2] Observations by the NEOWISE mission gave a larger diameter of 37.7 kilometers and an albedo of 0.041.[3] It has an absolute magnitude is 11.1.[1]