Holman, Matthew J., Payne, Matthew J., Fraser, Wesley, Lacerda, Pedro, Bannister, Michele T., Lackner, Michael, Chen, Ying-Tung, Lin, Hsing Wen, Smith, Kenneth W., Kokotanekova, Rosita, Young, David, Chambers, K., Chastel, S., Denneau, L., Fitzsimmons, A., Flewelling, H., Grav, Tommy, Huber, M., Induni, Nick, Kudritzki, Rolf-Peter, Krolewski, Alex, Jedicke, R., Kaiser, N., Lilly, E., Magnier, E. et al. 2018. "A Dwarf Planet Class Object in the 21:5 Resonance with Neptune." Astrophysical Journal Letters 855:L6. https://doi.org/10.3847/2041-8213/aaadb3
We report the discovery of an H r = 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 and 2016 provide an exceptionally well determined orbit for 2010 JO179, with a semimajor 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 100 Myr timescales, 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.