|Discovered by||C. J. van Houten
I. van Houten G.
|Discovery site||Palomar Obs.|
|Discovery date||24 September 1960|
|MPC designation||1868 Thersites|
|2008 P-L · 1972 RB2|
|Jupiter trojan 
|Orbital characteristics |
|Epoch 31 July 2016 (JD 2457600.5)|
|Uncertainty parameter 0|
|Observation arc||62.05 yr (22,663 days)|
|12.27 yr (4,482 days)|
|0° 4m 49.08s / day|
|Jupiter MOID||0.2025 AU|
|Jupiter Tisserand parameter||2.903|
|Dimensions||66.92 km (calculated)
±0.81 km 68.16
±2.02 km 78.89
1868 Thersites, provisional designation 2008 P-L, is a carbonaceous Jupiter trojan from the Greek camp, approximately 70 kilometers in diameter. It was discovered by Dutch astronomer couple Ingrid and Cornelis van Houten at Leiden, on photographic plates taken by Dutch-American astronomer Tom Gehrels at the U.S. Palomar Observatory, California, on 24 September 1960. On the same day, the group discovered another Jupiter trojan, 1869 Philoctetes.
The dark C-type asteroid is orbiting in the leading Greek camp at Jupiter's L4 Lagrangian point, 60° ahead of its orbit (see Trojans in astronomy). It orbits the Sun at a distance of 4.7–5.9 AU once every 12.27 years (4,482 days). Its orbit has an eccentricity of 0.11 and an inclination of 17° with respect to the plane of the ecliptic. The first precovery was taken at Palomar Observatory in 1954, extending the asteroid's observation arc by 6 years prior to its discovery.
In 1994, photometric observations of this asteroid were made by Stefano Mottola at ESO's La Silla Observatory, Chile, using the Dutch 0.9-metre Telescope. The observations were used to build a light-curve showing a rotation period of ±0.014 hours with a brightness variation of 10.416±0.01 0.14magnitude (U=2+). According to the space-based surveys carried out by the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, the asteroid's diameter measures 78.9 and 68.2 kilometers, respectively, with a low albedo of 0.055 for its surface. The Collaborative Asteroid Lightcurve Link assumes a standard albedo for carbonaceous asteroids of 0.057, and calculates a shorter diameter of 66.9 kilometers, based on an absolute magnitude of 9.6.
The provisional survey designation "P-L" stands for Palomar–Leiden, named after Palomar Observatory and Leiden Observatory, which collaborated on the fruitful Palomar–Leiden survey in the 1960s and 1970s. Gehrels used Palomar's Samuel Oschin telescope (also known as the 48-inch Schmidt Telescope), and shipped the photographic plates to Cornelis and Ingrid van Houten at Leiden Observatory, where astrometry was carried out. The trio are credited with the discovery of 4,620 minor planets.
The Trojan asteroid is named from Greek mythology after Thersites, a Greek warrior who wanted to abandon Troy's siege during the Trojan War and head home. The given name also refers to the fact, that the asteroid was discovered farthest from the L4 Lagrangian point. Naming citation was published before November 1977 (M.P.C. 3826).
- "JPL Small-Body Database Browser: 1868 Thersites (2008 P-L)" (2016-04-14 last obs.). Jet Propulsion Laboratory. Retrieved 21 May 2016.
- Schmadel, Lutz D. (2007). Dictionary of Minor Planet Names – (1868) Thersites. Springer Berlin Heidelberg. p. 150. ISBN 978-3-540-00238-3. Retrieved 1 March 2016.
- "LCDB Data for (1868) Thersites". Asteroid Lightcurve Database (LCDB). Retrieved 21 May 2016.
- "1868 Thersites (2008 P-L)". Minor Planet Center. Retrieved 1 March 2016.
- Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal. 741 (2): 25. arXiv:. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90. Retrieved 21 May 2016.
- Usui, Fumihiko; Kuroda, Daisuke; Müller, Thomas G.; Hasegawa, Sunao; Ishiguro, Masateru; Ootsubo, Takafumi; et al. (October 2011). "Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey". Publications of the Astronomical Society of Japan. 63 (5): 1117–1138. Bibcode:2011PASJ...63.1117U. doi:10.1093/pasj/63.5.1117. Retrieved 21 May 2016.
- Mottola, Stefano; Di Martino, Mario; Erikson, Anders; Gonano-Beurer, Maria; Carbognani, Albino; Carsenty, Uri; et al. (May 2011). "Rotational Properties of Jupiter Trojans. I. Light Curves of 80 Objects". The Astronomical Journal. 141 (5): 32. Bibcode:2011AJ....141..170M. doi:10.1088/0004-6256/141/5/170. Retrieved 1 March 2016.
- "Minor Planet Discoverers". Minor Planet Center. 24 April 2016. Retrieved 21 May 2016.
- "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 21 May 2016.
- Rotational Properties of Jupiter Trojans. I. Light Curves of 80 Objects, Motola, Martino and Erikson (PDF)
- Asteroid Lightcurve Database (LCDB), query form (info)
- Dictionary of Minor Planet Names, Google books
- Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend
- Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
- 1868 Thersites at the JPL Small-Body Database