 Orbit of 86 Semele on 1 Jan 2009 | |
| Discovery | |
|---|---|
| Discovered by | Friedrich Tietjen |
| Discovery date | January 4, 1866 |
| Designations | |
| (86) Semele | |
| Pronunciation | /ˈsɛmɪlə/[1] |
Named after | Semele |
| Main belt | |
| Adjectives | Semelean /sɛmɪˈleɪən/[2] |
| Orbital characteristics[3] | |
| Epoch December 31, 2006 (JD 2454100.5) | |
| Aphelion | 562.652 Gm (3.761 AU) |
| Perihelion | 369.116 Gm (2.467 AU) |
| 465.884 Gm (3.114 AU) | |
| Eccentricity | 0.208 |
| 2,007.366 d (5.50 a) | |
Average orbital speed | 16.69 km/s |
| 264.875° | |
| Inclination | 4.822° |
| 86.452° | |
| 307.886° | |
| Physical characteristics | |
| Dimensions | 120.6 km |
| Mass | 1.8×1018 kg |
Equatorial surface gravity | 0.0337 m/s² |
Equatorial escape velocity | 0.0638 km/s |
| 16.641±0.001 h[4] | |
| 0.047 [5] | |
| C | |
| 8.54 | |
Semele (minor planet designation: 86 Semele) is a large and very dark main-belt asteroid with an orbital period of 5.5 years. It is rotating with a period of 16.6 hours, and varies in magnitude by 0.13 during each cycle.[4] This object is classified as a C-type asteroid and is probably composed of carbonates.
Semele was discovered by German astronomer Friedrich Tietjen on January 4, 1866.[6] It was his first and only asteroid discovery. It is named after Semele, the mother of Dionysus in Greek mythology.
The orbit of 86 Semele places it in a 13:6 mean motion resonance with the planet Jupiter. The computed Lyapunov time for this asteroid is only 6,000 years, indicating that it occupies a chaotic orbit that will change randomly over time because of gravitational perturbations of the planets. This Lyapunov time is the second lowest among the first 100 named minor planets.[7]
