1868 Thersites

1868 Thersites

Discovery
Discovered by	C. J. van Houten I. van Houten G. T. Gehrels
Discovery site	Palomar Obs.
Discovery date	24 September 1960
Designations
MPC designation	1868 Thersites
Named after	Thersites (Greek mythology)
Alternative names	2008 P-L · 1972 RB2
Minor planet category	Jupiter trojan  (Greek camp)
Orbital characteristics
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc	62.05 yr (22,663 days)
Aphelion	5.8995 AU
Perihelion	4.74 AU
Semi-major axis	5.3197 AU
Eccentricity	0.109
Orbital period	12.27 yr (4,482 days)
Mean anomaly	229.3494°
Inclination	16.7539°
Longitude of ascending node	197.8417°
Argument of perihelion	169.5884°
Jupiter MOID	0.2025 AU
Physical characteristics
Dimensions	78.89±2.02 km 68.16±0.81 km 66.92 km (calculated)
Rotation period	10.416±0.014 h
Geometric albedo	0.055±0.003 0.055±0.008 0.057 (assumed)
Spectral type	C
Absolute magnitude (H)	9.6 9.30

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 10.416±0.014 hours with a brightness variation of 0.14±0.01 magnitude (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).

External links

• 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

• Discovery · Orbit diagram · Orbital elements · Physical parameters