37 Fides

Fides /ˈfaɪdiːz/ (minor planet designation: 37 Fides) is a large main-belt asteroid. It was discovered by German astronomer Karl Theodor Robert Luther on October 5, 1855, and named after Fides, the Roman goddess of loyalty. Fides was the last of the main-belt asteroids to be assigned an iconic symbol, a Latin cross U+271D ✝ (). 37 Fides is also a S-type asteroid in the Tholen classification system.

37 Fides

A three-dimensional model of 37 Fides based on its light curve
Discovery
Discovered by	R. Luther
Discovery date	October 5, 1855
Designations
Designation	(37) Fides
Pronunciation	/ˈfaɪdiːz/
Named after	Fides
Alternative names	1925 WH
Minor planet category	Main belt
Adjectives	Fidean /ˈfɪdiən/
Symbol	(historical)
Orbital characteristics
Epoch February 25, 2023 (JD 2460000.5)
Observation arc	167 yr
Aphelion	464.902 Gm (3.108 AU)
Perihelion	325.937 Gm (2.179 AU)
Semi-major axis	395.419 Gm (2.643 AU)
Eccentricity	0.176
Orbital period (sidereal)	1,569.628 d (4.30 a)
Mean anomaly	303.436°
Mean motion	0° 13m 45.84s / day
Inclination	3.071°
Longitude of ascending node	7.267°
Argument of perihelion	62.327°
Physical characteristics
Dimensions	108.35 ± 1.9 km
Mass	(1.674 ± 0.663/0.314)×1018 kg
Mean density	2.906 ± 1.150/0.545 g/cm3
Surface gravity	0.0381 m/s2
Escape velocity	0.0642 km/s
Synodic rotation period	0.3055 d (7.334 h)
Albedo	0.183 ± 0.007
Temperature	~167 K
Spectral type	S
Absolute magnitude (H)	7.41

Photometric observations of this asteroid at multiple observatories during 1981–82 gave an unusual light curve with three minima and maxima. The curve changed with varying phase angle of the asteroid relative to the viewer and the position of the Sun, indicating the changing influence of shadows cast by surface features. The composite light curve has a best fit period estimate of 7.33 hours. Austrian astronomer Hans Josef Schober has suggested that the multiple minima and maxima during each period may be an indication of a binary nature.