(36256) 1999 XT17

Main belt asteroid November 2025 yes (36256) 1999 XT 17 #D6D6D6 LINEAR 3 December 1999 Socorro, New Mexico, United States (36256) 1999 XT 17 1979 UU 31979 VH1989 TF 2 Main belt 21 November 2025 (JD 2461000.5) 0 3.3049 AU 2.5722 AU 2.9386 A2 0.1247 5.0374 yr (1839.9 d) 356.163° 31.122° 59.833° 10.9816° 0.1957° / d 2.0141 AU 3.235 10.21 0.32 km 4.108048 h 0.186 0.033 A-type3 12.54 (36256) 1999 XT 17 is an unnamed asteroid located in the main asteroid belt. Discovered on 3 December 1999 by the Lincoln Near-Earth Asteroid Research (LINEAR) program, it was initially observed as a lost asteroid in 1979. Around 10 km mi in size, it is the parent body of a small and unusual asteroid family. Many members of this asteroid family, including 1999 XT 17, are olivine-rich asteroids, suggesting that they may have originated from the mantle of a destroyed planetesimal. Discovery 1999 XT 17 was first observed by the Crimean Astrophysical Observatory on 16 October 1979 and was assigned the provisional designation 1979 UU 3 by the Minor Planet Center (MPC).18 It was observed by the Crimean Astrophysical Observatory again on 11 November of that year; believed to be a different object, it was assigned a second provisional designation, 1979 VH.19 It subsequently became a lost asteroid. It was briefly observed by Klet Observatory in October 1989, but was not identified as the object observed at the Crimean Astrophysical Observatory a decade earlier. The asteroid was observed again in late 1999 by the Lincoln Near-Earth Asteroid Research (LINEAR) program, located at the Experimental Test Site (ETS) in Socorro, New Mexico, United States. 3 December 1999 is marked as the official discovery date of the asteroid, and it was given its primary provisional designation 1999 XT 17. Once 1999 XT 17's orbit was sufficiently determined, it was assigned the number (36256) by the MPC on 27 February 2002. The MPC also linked the 1979 and 1989 observations to the asteroid that same day.437 2025, it is unnamed. Orbit thumb|left|Diagram of 1999 XT 17's orbit between Mars and Jupiter 1999 XT 17 orbits the Sun at an average distance—its semi-major axis—of 2.94 astronomical units (AU), placing it in the main asteroid belt. Along its 5.04 year long orbit, its distance from the Sun varies from 2.57 AU at perihelion to 3.31 AU at aphelion due to its orbital eccentricity of 0.12. The asteroid's orbit is inclined by 10.98° with respect to the ecliptic plane. Asteroid family 1999 XT 17 is the parent body of an asteroid family (FIN: 3029) with 661 identified members. The family lies near the outer edge of the "pristine zone", a region of the outer main belt bounded by the 5:2 and 7:3 mean motion resonances (MMRs) with Jupiter at 2.825 AU and 2.955 AU, respectively.2 This zone, whose name was coined in a 2013 study led by Miroslav Brož, is deficient in smaller asteroids. The bounding resonances prevent the migration of asteroids from outside the zone, and it may represent the primordial main belt population before the creation of large asteroid families.2, 10 The 1999 XT 17 family is unusually rich in olivine-bearing A-type asteroids. Of the 36 members that have a spectral classification, 44.4% are A-types—an abundance seven times higher than the main belt average.36 The second-most abundant spectral type found within the family is the S-complex, comprising 30.5% of the classified population.3 However, S-complex members of the family may have originated from other asteroid families, becoming interlopers of the 1999 XT 17 family. None of the five S-complex families residing within the pristine zone are close enough to the 1999 XT 17 family to contaminate it.The S-complex families in the pristine zone are associated with 158 Koronis, 832 Karin, 918 Itha, 10811 Lau, and (15477) 1999 CG 1. Instead, the Eos family is the likeliest source of contamination. The Eos family resides outside of the pristine zone, but some of its members migrated across the 7:3 Jovian MMR fast enough to avoid destabilization and now contaminate the pristine zone. A 2024 study led by M. Galinier noted that all of the 1999 XT 17 family's S-complex members have orbits similar to known Eos family migrants, suggesting that only the A-type members are truly related to each other. If the 1999 XT 17 family only consists of A-type asteroids, then it likely originated from the mantle of a partially or fully differentiated planetesimal.4–5 Physical properties 1999 XT 17 is estimated to be around 10.2 km mi in diameter, with a geometric albedo of 0.19. Photometric observations from the Asteroid Terrestrial-impact Last Alert System (ATLAS) suggests that it has a rotation period of 4.11 hours. Spectroscopic observations of 1999 XT 17 in the near-infrared show that it is an A-type asteroid in the Bus–DeMeo and Mahlke classification schemes.2 Comparison of 1999 XT 17's visible and near-infrared spectrum to meteorites with similar spectra suggests that it is mostly composed of pure olivine.5 Notes References (36256) = 1979 UU3 = 1979 VH = 1989 TF2 = 1999 XT17 https://www.minorplanetcenter.net/db_search/show_object?object_id=36256 Minor Planet Center 9 November 2025 (3618 obs) 2025-11-04 last obs. JPL Small-Body Database Lookup: 36256 (1999 XT17) https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=20036256 Jet Propulsion Laboratory 9 November 2025 M. P. C. 7072/7073 https://www.minorplanetcenter.net/iau/ECS/MPCArchive/1982/MPC_19820804.pdf Minor Planet Circulars Minor Planet Center 4 August 1982 7072/7073 18–19 9 November 2025 M. P. C. 44875 https://www.minorplanetcenter.net/iau/ECS/MPCArchive/2002/MPC_20020227.pdf Minor Planet Circulars Minor Planet Center 27 February 2002 44875 193 9 November 2025 M. P. O. 24505 https://www.minorplanetcenter.net/iau/ECS/MPCArchive/2002/MPO_20020227.pdf Minor Planets and Comets Orbit Supplement Minor Planets Center 27 February 2002 24505 9 November 2025 Galinier M. Delbo M. Avdellidou C. Galluccio L. Discovery of the first olivine-dominated A-type asteroid family March 2024 Astronomy & Astrophysics 683 L3 L3 10.1051/0004-6361/202349057 free 2024A&A...683L...3G Brož M. Morbidelli A. Bottke W. F. Rozehnal J. Vokrouhlický D. Nesvorný D. Constraining the cometary flux through the asteroid belt during the late heavy bombardment March 2013 Astronomy & Astrophysics 551 A117 A117 10.1051/0004-6361/201219296 free 1301.6221 2013A&A...551A.117B Delbo Marco Avdellidou Chrysa Galinier Marjorie Bhat Ullas Dyer Thomas Bolin Bryce T. Galluccio Laurent Gaia and IRTF abundance of A-type main belt asteroids November 2025 astro-ph.EP 2511.00902 Nesvorný David 2026-03-23 A Census before Rubin of Asteroid Families in the Main Belt https://iopscience.iop.org/article/10.3847/1538-4365/ae4bd4 The Astrophysical Journal Supplement Series 283 2 63 10.3847/1538-4365/ae4bd4 free 0067-0049 External links 36256 1999XT17 36256 36256 36256 19991203 Category:A-type asteroids