133 Cyrene

133 Cyrene is a fairly large and very bright main-belt asteroid that was discovered by J. C. Watson on 16 August 1873 in Ann Arbor, Michigan, and named after Cyrene, a nymph, daughter of king Hypseus and beloved of Apollo in Greek mythology.^[7] It is classified as an S-type asteroid based upon its spectrum. It is listed as a member of the Hecuba group of asteroids that orbit near the 2:1 mean-motion resonance with Jupiter.^[8]

133 Cyrene

Orbital diagram
Discovery
Discovered by	James Craig Watson
Discovery date	16 August 1873
Designations
MPC designation	(133) Cyrene
Pronunciation	/saɪˈriːniː/[1]
Named after	Cyrene (nymph)
Alternative designations	A873 QA; 1910 NB; 1936 HO; 1948 QC; 1959 UR
Minor planet category	Main belt
Adjectives	Cyrenean /saɪrɪˈniːən/, Cyrenian /saɪˈriːniən/[2]
Orbital characteristics[3]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc	142.65 yr (52104 d)
Aphelion	3.48274 AU (521.010 Gm)
Perihelion	2.64706 AU (395.995 Gm)
Semi-major axis	3.06490 AU (458.503 Gm)
Eccentricity	0.13633
Orbital period (sidereal)	5.37 yr (1959.9 d)
Average orbital speed	17.03 km/s
Mean anomaly	316.166°
Mean motion	0° 11m 1.273s / day
Inclination	7.21561°
Longitude of ascending node	319.066°
Argument of perihelion	289.646°
Earth MOID	1.64415 AU (245.961 Gm)
Jupiter MOID	1.65199 AU (247.134 Gm)
TJupiter	3.206
Physical characteristics
Dimensions	66.57±6.0 km
Mass	3.1 × 1017 kg
Mean density	2.0? g/cm3
Equatorial surface gravity	0.0186 m/s²
Equatorial escape velocity	0.0352 km/s
Synodic rotation period	12.708 h (0.5295 d)[3] 12.707 h (0.5295 d)[4]
Geometric albedo	0.2563±0.053[3] 0.2563[5]
Temperature	~133 K
Spectral type	S[5]
Absolute magnitude (H)	7.98,[3] 7.990[6]

In the Tholen classification system, it is categorized as a stony SR-type asteroid.^[9] Photometric observations of this asteroid at the Altimira Observatory in 1985 gave a light curve with a period of 12.707 ± 0.015 hours and a brightness variation of 0.22 in magnitude. This result matches previous measurements reported in 1984 and 2005.^[4]