|Discovery site||Kitt Peak National Obs.|
|Discovery date||6 November 1985|
|MPC designation||(3801) Thrasymedes|
|Jupiter trojan |
Greek  · background 
|Orbital characteristics |
|Epoch 23 March 2018 (JD 2458200.5)|
|Uncertainty parameter 0|
|Observation arc||63.25 yr (23,102 d)|
|12.28 yr (4,486 d)|
|0° 4m 48.72s / day|
|Jupiter MOID||0.0096 AU|
3801 Thrasymedes (// THRAS-ə-MEE-deez), provisional designation 1985 VS, is a mid-sized Jupiter trojan from the Greek camp, approximately 34 kilometers (21 miles) in diameter. It was discovered on 6 November 1985, by astronomers with the Spacewatch survey at the Kitt Peak National Observatory in Arizona, United States. The dark Jovian asteroid has a rotation period of 20.3 hours and forms an asteroid pair with 1583 Antilochus. It was named after Thrasymedes from Greek mythology.
Orbit and classification
Thrasymedes is a dark Jovian asteroid in a 1:1 orbital resonance with Jupiter. It is located in the leading Greek camp at the Gas Giant's L4 Lagrangian point, 60° ahead on its orbit . It is also a non-family asteroid of the Jovian background population. It orbits the Sun at a distance of 5.2–5.4 AU once every 12 years and 3 months (4,486 days; semi-major axis of 5.32 AU). Its orbit has an eccentricity of 0.02 and an inclination of 28° with respect to the ecliptic.
In 1993, Andrea Milani suggested that Thrasymedes forms an asteroid pair with 1583 Antilochus, using the hierarchical clustering method (HCM), which looks for groupings of neighboring asteroids based on the smallest distances between them in the proper orbital element space. Asteroid pairs, which at some point in the past had very small relative velocities, are typically formed by a collisional break-up of a parent body. Alternatively, they may have been former binary asteroids which became gravitationally unbound and are now following similar but different orbits around the Sun.
The astronomer describes the finding as statistically significant though difficult to account for by a regular collisional event.[a] The Antilochus–Thrasymedes pair is not listed at the Johnston's archive.
In 2015, photometric observations by the Kepler space telescope gave two lightcurves. The best-rated one showed a period of 20.270±0.672 hours and a brightness variation of 0.14 magnitude (U=2/2-). In June 2016, another period determination from 16 nights of observation by Robert Stephens at the Center for Solar System Studies in California gave a divergent 49.55±0.02 hours with a notably large amplitude of 1.07 magnitude (U=2).[b]
Diameter and albedo
According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Thrasymedes measures 34.28 kilometers in diameter and its surface has an albedo of 0.066, while he Collaborative Asteroid Lightcurve Link assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a diameter of 35.12 kilometers based on an absolute magnitude of 11.0.
This minor planet was named after the Greek warrior Thrasymedes, commander of 15 ships to Troy. He is the son of Nestor and brother of Antilochus, who was killed during a fight with Memnon. He was also one of the 30 warriors to enter the wooden Trojan Horse.
The official naming citation was published by the Minor Planet Center on 31 May 1988 (M.P.C. 13179). The citation also mentions that this Jovian asteroids may have a common origin with 1583 Antilochus, because their orbits are very similar.
- Besides the asteroid pair Antilochus—Thrasymedes, Milani found five potential asteroid families in the Greek camp, clustered around the Jovian asteroids 1437 Diomedes, 1647 Menelaus, 2456 Palamedes, 2797 Teucer and (4035) 1986 WD (Milani 1993, p. 94).
- Lightcurve plot of (3801) Thrasymedes from Jun 2016 with a period of 49.55±0.02 and Δmag of 1.07, taken by Robert Stephens at the Center for Solar System Studies (U81). Quality code is 2+ (lightcurve rating at CS3). Summary figures at the LCDB and CS3.
- "3801 Thrasymedes (1985 VS)". Minor Planet Center. Retrieved 21 June 2018.
- "JPL Small-Body Database Browser: 3801 Thrasymedes (1985 VS)" (2017-07-03 last obs.). Jet Propulsion Laboratory. Retrieved 21 June 2018.
- "List of Jupiter Trojans". Minor Planet Center. 1 June 2018. Retrieved 21 June 2018.
- "Asteroid (3801) Thrasymedes – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 21 June 2018.
- Grav, T.; Mainzer, A. K.; Bauer, J. M.; Masiero, J. R.; Nugent, C. R. (November 2012). "WISE/NEOWISE Observations of the Jovian Trojan Population: Taxonomy". The Astrophysical Journal. 759 (1): 10. arXiv:1209.1549. Bibcode:2012ApJ...759...49G. doi:10.1088/0004-637X/759/1/49. Retrieved 21 June 2018. (online catalog)
- Szabó, Gy. M.; Pál, A.; Kiss, Cs.; Kiss, L. L.; Molnár, L.; Hanyecz, O.; et al. (March 2017). "The heart of the swarm: K2 photometry and rotational characteristics of 56 Jovian Trojan asteroids" (PDF). Astronomy and Astrophysics. 599: 13. arXiv:1609.02760. Bibcode:2017A&A...599A..44S. doi:10.1051/0004-6361/201629401. Retrieved 21 June 2018.
- "LCDB Data for (3801) Thrasymedes". Asteroid Lightcurve Database (LCDB). Retrieved 21 June 2018.
- Milani, Andrea (October 1993). "The Trojan asteroid belt: Proper elements, stability, chaos and families". Celestial Mechanics and Dynamical Astronomy. 57: 59–94. Bibcode:1993CeMDA..57...59M. doi:10.1007/BF00692462. ISSN 0923-2958. Retrieved 30 June 2018.
- Johnston, Wm. Robert (29 April 2018). "Asteroid pairs and clusters". Johnston's Archive. Retrieved 30 June 2018.
- Melita, M. D.; Duffard, R.; Williams, I. P.; Jones, D. C.; Licandro, J.; Ortiz, J. L. (June 2010). "Lightcurves of 6 Jupiter Trojan asteroids". Planetary and Space Science. 58 (7–8): 1035–1039. Bibcode:2010P&SS...58.1035M. doi:10.1016/j.pss.2010.03.009. Retrieved 21 June 2018.
- Duffard, R. D.; Melita, M.; Ortiz, J. L.; Licandro, J.; Williams, I. P.; Jones, D. (December 2007). "Light-Curve Survey of the Trojan Asteroids" (PDF). Asteroids. Bibcode:2008LPICo1405.8187D. Retrieved 5 July 2018.
- Ryan, Erin Lee; Sharkey, Benjamin N. L.; Woodward, Charles E. (March 2017). "Trojan Asteroids in the Kepler Campaign 6 Field". The Astronomical Journal. 153 (3): 12. Bibcode:2017AJ....153..116R. doi:10.3847/1538-3881/153/3/116. Retrieved 21 June 2018.
- "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 21 June 2018.
- Asteroid Lightcurve Database (LCDB), query form (info)
- Dictionary of Minor Planet Names, Google books
- Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
- Asteroid 3801 Thrasymedes at the Small Bodies Data Ferret
- 3801 Thrasymedes at AstDyS-2, Asteroids—Dynamic Site
- 3801 Thrasymedes at the JPL Small-Body Database