617 Patroclus
617 Patroclus (/pəˈtroʊkləs/ pə-TROH-kləs) is a large binary Jupiter trojan asteroid. It is a dark D-type asteroid and a slow rotator, due to the 103-hour orbital period of its two components. It is one of five Jupiter trojan asteroids targeted by the Lucy space probe, and is scheduled for a flyby in 2033.
Hubble Space Telescope image composite of Patroclus and its companion Menoetius, taken in 2018 | |
| Discovery | |
|---|---|
| Discovered by | A. Kopff |
| Discovery site | Heidelberg Obs. |
| Discovery date | 17 October 1906 |
| Designations | |
MPC designation | (617) Patroclus |
| Pronunciation | /pəˈtroʊkləs/ |
Named after | Πάτροκλος Patroklos (Greek mythology) |
Alternative designations | 1906 VY · 1941 XC 1962 NB |
Minor planet category | Jupiter trojan Trojan · background |
| Adjectives | Patroclean /pætrəˈkliːən/ |
| Orbital characteristics | |
| Epoch 25 February 2023 (JD 2460000.5) | |
| Uncertainty parameter 0 | |
| Aphelion | 5.937 AU |
| Perihelion | 4.480 AU |
Semi-major axis | 5.209 AU |
| Eccentricity | 0.1399 |
Orbital period (sidereal) | 11.89 yr (4,342 d) |
Mean anomaly | 319.506° |
Mean motion | 0° 4m 58.464s / day |
| Inclination | 22.062° |
Longitude of ascending node | 44.360° |
| 308.306° | |
| Known satellites | 1 (Menoetius) |
| Jupiter MOID | 0.1868 AU |
| TJupiter | 2.835 |
| Physical characteristics | |
| Dimensions | 127 km × 117 km × 98 km (primary only) |
Mean diameter | 113±3 km (primary only) 140.36±0.87 km 140.85±3.37 km 140.92±4.7 km 143.14±8.37 km 154 km |
| Volume | 1.36×106 km3 |
| Mass | (1.36±0.11)×1018 kg 1.20×1018 kg |
Mean density | 0.88±0.17 g/cm3 |
Synodic rotation period | 102.8 h 102 h 103.02±0.40 h 103.5±0.3 h |
| 0.047±0.003 | |
| D (Tholen) C0 (Barucci) D (Tedesco) U–B = 0.215±0.045 B–V = 0.710±0.050 V–R = 0.420±0.030 V–I = 0.830±0.020 | |
| 8.18 | |
Patroclus was discovered on 17 October 1906, by astronomer August Kopff at the Heidelberg Observatory in Germany, and was named after Patroclus in Greek mythology. It was the second trojan to be discovered and the only member of the Trojan camp named after a Greek figure, as the convention of naming one 'camp' after Greek figures of the Trojan War and the other after Trojan figures had not yet been established.
Patroclus was long thought to be one of the largest Jupiter trojans, with a diameter on the order of 150 km. However, in 2001 it was discovered to be a binary asteroid of two similarly sized objects. The name Patroclus is now assigned to the larger component, some 110–115 km in diameter, while the secondary, slightly smaller at 100–105 km in diameter, has been named Menoetius (/mɪˈniːʃəs/ mə-NEE-shəs). This was the first discovery of a binary trojan asteroid.