, 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.
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.
Details
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. 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. 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.
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.
References
External links
Trans-Neptunian objects
Centaurs (small Solar System bodies) Damocloids Discoveries by MLS 20110531 Minor planets with a retrograde orbit