Minorplanet: | yes |
Background: |
|
Discoverer: | Mount Lemmon Srvy. |
Discovery Site: | Mount Lemmon Obs. |
Discovered: | 31 May 2011 |
Alt Names: | Niku |
Named After: | A Chinese adjective meaning "rebellious" |
Mp Category: | TNOcentaur damocloid |
Epoch: | JD 2457600.5 |
Uncertainty: | 2 |
Observation Arc: | 1779 days (4.87 yr) |
Aphelion: | 47.427 AU |
Perihelion: | 23.7805 AU |
Semimajor: | 35.604 AU |
Eccentricity: | 0.33208 |
Period: | 212.45 years |
Inclination: | 110.1537° |
Asc Node: | 243.77772° |
Arg Peri: | 322.174° |
Mean Anomaly: | 29.487° |
Tisserand: | −1.552 |
Mean Diameter: | 75–250 km 161 km |
Abs Magnitude: | 7.2[1] |
Magnitude: | 22[2] |
, nicknamed Niku, is a trans-Neptunian object whose orbit is tilted 110° with respect to the planets' orbital plane. Thus, it has a nearly polar retrograde orbit around the Sun.[3] [4] [5] [6]
While the object has not received a formal name, it received the moniker "Niku" (逆骨), meaning "rebellious" in the Chinese language, by its discoverers.[7] [8]
was discovered by the Mount Lemmon Survey on 31 May 2011. Its rediscovery was announced in August 2016 by a team of astronomers using the Pan-STARRS telescope. It was soon linked with a supposed prograde centaur (; inclination = 38° and semi-major axis = 28 AU) that had been lost due to a short observation arc.[4] is in a 7:9 resonance with Neptune. Currently it is the only object with a nearly polar orbit that is in resonance with a planet.[9] Notably, it is part of a group of objects that orbit the Sun in a highly inclined orbit; the reasons for this unusual orbit are unknown as of August 2016.[10]
The orbital characteristics of have been compared to those of (Drac). The orbits of,,,,,, appear to occupy a common plane, with three in prograde and three in retrograde orbits. The probability of this alignment occurring by chance is 0.016%. These orbits should leave a common plane in a few million years because the precession of prograde and retrograde orbits are in opposite directions. Simulations including the hypothetical Planet Nine did not maintain a common orbital plane and the plane does not coincide with the plane of the predicted high-inclination large semi-major axis objects of that model. Other simulations with a few Earth-mass dwarf planet on a high-inclination orbit also failed to reproduce the alignment.[4]