| Minorplanet: | yes |
| Background: |
|
| 86 Semele | |
| Discovered: | 4 January 1866 |
| Mpc Name: | (86) Semele |
| Pronounced: | [1] |
| Adjective: | Semelean [2] |
| Epoch: | 31 December 2006 (JD 2454100.5) |
| Semimajor: | 465.884 Gm (3.114 AU) |
| Perihelion: | 369.116 Gm (2.467 AU) |
| Eccentricity: | 0.208 |
| Period: | 2007.366day |
| Inclination: | 4.822° |
| Asc Node: | 86.452° |
| Arg Peri: | 307.886° |
| Mean Anomaly: | 264.875° |
| Avg Speed: | 16.69 km/s |
| Dimensions: | 120.6 km |
| Mass: | 1.8 kg |
| Surface Grav: | 0.0337 m/s² |
| Escape Velocity: | 0.0638 km/s |
| Abs Magnitude: | 8.54 |
| Albedo: | 0.047 [3] |
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. This object is classified as a C-type asteroid and is probably composed of carbonates.
Semele was discovered by German astronomer Friedrich Tietjen on 4 January 1866. 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.