103 Hera

103 Hera is a moderately large main-belt asteroid with an orbital period of 4.44 years. It was discovered by Canadian-American astronomer James Craig Watson on September 7, 1868,^[6] and named after Hera, queen and fifth in power of the Olympian gods in Greek mythology. This is a stony S-type asteroid^[5] with a silicate surface composition.

103 Hera

3D convex shape model of 103 Hera
Discovery
Discovered by	James Craig Watson[1]
Discovery date	7 September 1868[1]
Designations
MPC designation	(103) Hera
Pronunciation	/ˈhɪərə/[2]
Named after	Hera
Alternative designations	A868 RA, 1927 CV 1950 CM
Minor planet category	Main belt
Orbital characteristics[3]
Epoch 31 July 2016 (JD 2457600.5)[1]
Uncertainty parameter 0
Observation arc	144.99 yr (52958 d)
Aphelion	2.92042 AU (436.889 Gm)[1]
Perihelion	2.48175 AU (371.265 Gm)[1]
Semi-major axis	2.70109 AU (404.077 Gm)[1]
Eccentricity	0.0812034[1]
Orbital period (sidereal)	4.44 yr (1621.5 d)[1]
Average orbital speed	18.09 km/s
Mean anomaly	133.341°
Mean motion	0° 13m 19.279s / day
Inclination	5.41957°
Longitude of ascending node	136.186°
Argument of perihelion	188.361°
Earth MOID	1.46898 AU (219.756 Gm)
Jupiter MOID	2.32392 AU (347.653 Gm)
TJupiter	3.356
Physical characteristics
Dimensions	91.20±5.6 km
Mass	7.9×1017 kg
Equatorial surface gravity	0.0255 m/s²
Equatorial escape velocity	0.0482 km/s
Synodic rotation period	23.740 h (0.9892 d)[3] 0.9892 d[4]
Geometric albedo	0.1833±0.025
Temperature	~170 K
Spectral type	S[5]
Absolute magnitude (H)	7.66

Photometric observations made in 2010 at the Organ Mesa Observatory at Las Cruces, New Mexico, and the Hunters Hill Observatory at Ngunnawal, Australian Capital Territory, give a synodic rotation period of 23.740±0.001 h. The bimodal light curve shows a maximum brightness variation of 0.45 ± 0.03 in magnitude.^[4]

Measurements made with the IRAS observatory give a diameter of 91.58±4.14 km and a geometric albedo of 0.19±0.02. By comparison, the MIPS photometer on the Spitzer Space Telescope gives a diameter of 88.30±8.51 km and a geometric albedo of 0.20±0.04. When the asteroid was observed occulting a star, the chords showed a diameter of 89.1±1.1 km.^[7]