86 Semele

86 Semele

Discovery
Discovered by	Friedrich Tietjen
Discovery date	January 4, 1866
Designations
Named after	Semele
Minor planet category	Main belt
Orbital characteristics
Epoch December 31, 2006 (JD 2454100.5)
Aphelion	562.652 Gm (3.761 AU)
Perihelion	369.116 Gm (2.467 AU)
Semi-major axis	465.884 Gm (3.114 AU)
Eccentricity	0.208
Orbital period
Average orbital speed	16.69 km/s
Mean anomaly	264.875°
Inclination	4.822°
Longitude of ascending node	86.452°
Argument of perihelion	307.886°
Physical characteristics
Dimensions	120.6 km
Mass	1.8×1018 kg
Surface gravity	0.0337 m/s²
Escape velocity	0.0638 km/s
Albedo	0.047
Temperature	~158 K
Spectral type	C
Absolute magnitude (H)	8.54

86 Semele (/ˈsɛmᵻliː/ SEM-i-lee) is a large and very dark main-belt asteroid. It is probably composed of carbonates. Semele was discovered by German astronomer Friedrich Tietjen on January 4, 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.