(118378) 1999 HT11

Trans-Neptunian object September 2021 yes (118378) 1999 HT 11 #C2E0FF Kitt Peak National Obs. Kitt Peak National Obs. 17 April 1999 (118378) 1999 HT 11 TNOres (4:7) 1 July 2021 (JD 2459396.5) 3 20.78 yr (7,589 d) 49.001 AU 38.734 AU 43.868 AU 0.1170 290.55 yr (106,124 d) 328.33° 0.0034 ms / day 5.0489° 87.954° 189.27° 134 km (est. at 0.09) RR (very red) B–V 1.150 0.064 V–R 0.670 0.040 B–R 1.820 0.050 23.42 7.6 (118378) 1999 HT 11 is a trans-Neptunian object from the outermost region of the Solar System, locked in a 4:7 orbital resonance with Neptune. It was discovered on 17 April 1999, by astronomers at the Kitt Peak Observatory, Arizona, in the United States. The very red object measures approximately 134 km mi off 2 us in diameter. Discovery 1999 HT 11 was first observed on the night of 17 April 1999, by astronomers using the 4-meter Nicholas U. Mayall Telescope at Kitt Peak National Observatory in Arizona. Five additional objects were discovered on the same weekend: 129772 1999 HR 11, 1999 HS 11, 1999 HU 11 (Deucalion), 1999 HV 11 and 181874 1999 HW 11. The observing astronomers were Robert Millis, James Elliot, Matthew Holman, Mark Wagner as well as Kim Falinski. Follow-up observations with the Nordic Optical Telescope at the Roque de los Muchachos Observatory, La Palma, Spain, were made three weeks later. The body's observation arc begins with its official discovery observation at Kitt Peak on 17 April 1999. Orbit and classification This minor planet orbits the Sun at a distance of 38.7–49.0 AU once every 290 years and 7 months (106,124 days; semi-major axis of 43.87 AU). Its orbit has an eccentricity of 0.12 and an inclination of 5° with respect to the ecliptic. 2021, it is at 39.7 AU from the Sun with an apparent magnitude of 23.42, and will come to perihelion in 2047. 1999 HT 11 is a resonant trans-Neptunian object that stays in a 4:7 mean-motion orbital resonance with Neptune, orbiting exactly four times the Sun for every seven orbits Neptune does and are therefore protected from the planets scattering effect. The classification is deemed secure. The 4:7 resonance is located in the midst of the classical objects of the Kuiper belt, a circumstellar disc of otherwise non-resonant bodies, contrary to the more prominent resonant plutinos (2:3) and twotinos (1:2) which form the inner and outer rim of the Kuiper belt, respectively. Numbering and naming This minor planet was numbered by the Minor Planet Center on 16 November 2005, receiving the number 118378 118378 in the minor planet catalog (M.P.C. 55526). 2025, it has not been named. According to the established naming conventions, it will be given a mythological name associated with the underworld or with creation. Physical characteristics 1999 HT 11 has a very red surface color (RR) in the visible part of the spectrum, with B−V and V–R color indices of 1.150 0.064 and 0.670 0.040, respectively, for a combined B−R magnitude of 1.820 0.050. A red surface color is typically associated with the presence of tholins, polymer-like organic compounds, formed by long exposures to solar and cosmic radiation. Based on a generic magnitude-to-diameter conversion, 1999 HT 11 measures approximately 134 km mi off 2 us in diameter, for an assumed albedo of 0.9 and a magnitude of 7.6. According to Mike Brown, who estimates a mean-diameter of 137 km mi on 2 us, the object is too small for being considered a dwarf planet candidate ("probably not"). As of 2021, no rotational lightcurve for this body has been obtained from photometric observations. Its rotation period, pole and shape remain unknown. References 30em 2020-01-26 last obs. JPL Small-Body Database Browser: 118378 (1999 HT11) https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2118378 Jet Propulsion Laboratory 11 September 2021 118378 (1999 HT11) Minor Planet Center https://www.minorplanetcenter.net/db_search/show_object?object_id=118378 11 September 2021 MPC/MPO/MPS Archive Minor Planet Center https://www.minorplanetcenter.net/iau/ECS/MPCArchive/MPCArchive_TBL.html 11 September 2021 Naming of Astronomical Objects – Minor planets IAU – International Astronomical Union https://www.iau.org/public/themes/naming/#minorplanets 11 September 2021 31 October 2013 https://web.archive.org/web/20131031154417/https://www.iau.org/public/themes/naming/#minorplanets dead 118378 11 September 2021 Sheppard Scott S. December 2012 The Color Differences of Kuiper Belt Objects in Resonance with Neptune The Astronomical Journal 144 6 169 2012AJ....144..169S 0004-6256 10.1088/0004-6256/144/6/169 1210.0537 53746049 Asteroid (118378) 1999 HT11 – Ephemerides AstDyS-2, Asteroids – Dynamic Site https://newton.spacedys.com/astdys/index.php?pc=1.1.3.0&n=118378 11 September 2021 List of Known Trans-Neptunian Objects Johnston's Archive 18 August 2020 http://www.johnstonsarchive.net/astro/tnoslist.html 11 September 2021 Asteroid Size Estimator CNEOS NASA/JPL https://cneos.jpl.nasa.gov/tools/ast_size_est.html 11 September 2021 Orbit Fit and Astrometric record for 118378 Southwest Research Institute https://www.boulder.swri.edu/~buie/kbo/astrom/118378.html 11 September 2021 (The Deep Ecliptic Survey Object Classifications) How many dwarf planets are there in the outer solar system? California Institute of Technology Brown Michael E. http://web.gps.caltech.edu/~mbrown/dps.html 11 September 2021 MPEC 1999-K12 : SIX TNOs (including J99H11T) Minor Planet Electronic Circular Minor Planet Center 19 May 1999 https://www.minorplanetcenter.net/mpec/J99/J99K12.html 9 September 2021 External links List of Transneptunian Objects, Minor Planet Center (118378) 1999 HT11, Small Bodies Data Ferret Discovery Circumstances: Numbered Minor Planets (115001)-(120000), Minor Planet Center 118378 118378 (118378) 1999 HT 11 (118379) 1999 HC12 118378 118378 19990417