2015 KE172

2015 KE172, internal designation o5m72, is a distant resonant trans-Neptunian object on an eccentric orbit in the outermost region of the Solar System, approximately 100 kilometers (60 miles) in diameter. It was first observed on 21 May 2015 by astronomers with the Outer Solar System Origins Survey at the Mauna Kea Observatories on the island of Hawaii, United States.[1] It came to perihelion (closest approach to the Sun) in October 2017 at a distance of 44.1 AU (6.60 billion km).[2] Its existence was first released in February 2018, and the observations and orbit were announced on 27 April 2018.[5] It belongs to the most distant resonant objects known to exist.[3]

2015 KE172
Discovery[1]
Discovered byOSSOS
Discovery siteMauna Kea Obs.
Discovery date21 May 2015
(first observed only)
Designations
2015 KE172
o5m72
TNO[2] · 1:9[3]
distant[1]
Orbital characteristics[2]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 4
Observation arc3.26 yr (1,189 d)
Earliest precovery date30 May 2014
Aphelion222.11 AU (33.227 Tm)
Perihelion44.137 AU (6.6028 Tm)
133.12 AU (19.914 Tm)
Eccentricity0.6685
1536 yr (561,018 d)
0.1061°
0° 0m 2.16s / day
Inclination38.280°
227.55°
15.428°
Physical characteristics
Mean diameter
100 km (est. at 0.09)[4]
0.09 (generic est.)[4]
8.2024[2]

    Description
    Orbital diagram of 2015 KE172

    2015 KE172 is one of two known resonant trans-Neptunian objects that stay in a distant 1:9 resonance with the ice giant Neptune.[3] The other object is 2007 TC434 which was announced on 20 February 2018.[3][6][7][8] They are currently the most distant resonant objects known with a secure resonant classification, and their detection allowed to estimate a 1:9-resonant population of 11 thousand objects with similar orbits and similar size.[3] It is thought that both objects originated from the scattered disc before they became locked into a mean-motion resonance with Neptune.[3]

    Based on a generic magnitude-to-diameter conversion, the object measures 100 kilometers in diameter,[4] for an absolute magnitude of 8.2,[2] and an assumed albedo of 0.09, which is a typical figure seen among the diverse populations of distant objects.

    It orbits the Sun at a distance of 44.1–222 AU once every 1536 years (semi-major axis of 133.1 AU). Its orbit has a high eccentricity of 0.67 and an inclination of 38° with respect to the ecliptic.[2] As of 2018, this minor planet has not been numbered.[1]

    References
    1. "2015 KE172". Minor Planet Center. Retrieved 28 April 2018.
    2. "JPL Small-Body Database Browser: (2015 KE172)" (2017-08-31 last obs.). Jet Propulsion Laboratory. Retrieved 28 April 2018.
    3. Volk, Kathryn; Murray-Clay, Ruth A.; Gladman, Brett J.; Lawler, Samantha M.; Yu, Tze Yeung Mathew; Alexandersen, Mike; et al. (2018). "OSSOS IX: two objects in Neptune's 9:1 resonance -- implications for resonance sticking in the scattering population". The Astronomical Journal. 155 (6): 260. arXiv:1802.05805. Bibcode:2018AJ....155..260V. doi:10.3847/1538-3881/aac268. S2CID 119406588.
    4. "Asteroid Size Estimator". CNEOS NASA/JPL. Retrieved 28 April 2018.
    5. "MPEC 2018-H97 : 2015 KE172". IAU Minor Planet Center. 27 April 2018. Retrieved 28 April 2018. (K15KH2E)
    6. "MPEC 2018-D29 : 2007 TC434". IAU Minor Planet Center. 20 February 2018. Retrieved 28 April 2018. (K07Th4C)
    7. "2007 TC434". Minor Planet Center. Retrieved 28 April 2018.
    8. Orbit Fit and Astrometric record for 07TC434

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