We report the discovery of a Hr=3.4±0.1 dwarf planet candidate by the Pan-STARRS Outer Solar System Survey. 2010 JO179 is red with (g−r)=0.88±0.21, roughly round, and slowly rotating, with a period of 30.6 hr. Estimates of its albedo imply a diameter of 600--900~km. Observations sampling the span between 2005--2016 provide an exceptionally well-determined orbit for 2010 JO179, with a semi-major axis of 78.307±0.009 au, distant orbits known to this precision are rare. We find that 2010 JO179 librates securely within the 21:5 mean-motion resonance with Neptune on hundred-megayear time scales, joining the small but growing set of known distant dwarf planets on metastable resonant orbits. These imply a substantial trans-Neptunian population that shifts between stability in high-order resonances, the detached population, and the eroding population of the scattering disk.
@article{arxiv.1709.05427,
title = {A dwarf planet class object in the 21:5 resonance with Neptune},
author = {Matthew J. Holman and Matthew J. Payne and Wesley Fraser and Pedro Lacerda and Michele T. Bannister and Michael Lackner and Ying-Tung Chen and Hsing Wen Lin and Kenneth W. Smith and Rositako Kotanekova and David Young and K. Chambers and S. Chastel and L. Denneau and A. Fitzsimmons and H. Flewelling and Tommy Grav and M. Huber and Nick Induni and Rolf-Peter Kudritzki and Alex Krolewski and R. Jedicke and N. Kaiser and E. Lilly and E. Magnier and Zachary Mark and K. J. Meech and M. micheli and Daniel Murray and Alex Parker and Pavlos Protopapas and Darin Ragozzine and Peter Veres and R. Wainscoat and C. Waters and R. Weryk},
journal= {arXiv preprint arXiv:1709.05427},
year = {2018}
}