1919 Clemence

1919 Clemence, provisional designation 1971 SA, is a bright Hungaria asteroid and suspected tumbler from the inner regions of the asteroid belt, approximately 4 kilometers in diameter. It was discovered on 16 September 1971, by American astronomer James Gibson together with Argentine astronomer Carlos Cesco at the Yale-Columbia Southern Station at Leoncito Astronomical Complex in Argentina.^[3] It is named after astronomer Gerald Clemence.^[2]

1919 Clemence

Discovery[1]
Discovered by	J. Gibson C. U. Cesco
Discovery site	El Leoncito
Discovery date	16 September 1971
Designations
MPC designation	(1919) Clemence
Named after	Gerald Clemence (astronomer)[2]
Alternative designations	1971 SA · 1970 EA1 1971 QZ
Minor planet category	main-belt · (inner)[1] Hungaria[3][4]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	46.23 yr (16,884 days)
Aphelion	2.1200 AU
Perihelion	1.7522 AU
Semi-major axis	1.9361 AU
Eccentricity	0.0950
Orbital period (sidereal)	2.69 yr (984 days)
Mean anomaly	286.44°
Mean motion	0° 21m 57.24s / day
Inclination	19.337°
Longitude of ascending node	357.00°
Argument of perihelion	99.880°
Physical characteristics
Dimensions	3.238±0.015 km[5] 3.276±0.010[6] 4.95 km (calculated)[4]
Synodic rotation period	67.4±0.1 h (revised)[7] 68.5±0.1 h (original)[8]
Geometric albedo	0.3 (assumed)[4] 0.686±0.108[6] 0.7103±0.0672[5]
Spectral type	Tholen = X[1] X[4] · E[5] B–V = 0.750[1] U–B = 0.254[1]
Absolute magnitude (H)	13.45[1][4][5]

Orbit and classification

Clemence is a member of the Hungaria family, which form the innermost dense concentration of asteroids in the Solar System. It orbits the Sun at a distance of 1.8–2.1 AU once every 2 years and 8 months (984 days). Its orbit has an eccentricity of 0.10 and an inclination of 19° with respect to the ecliptic.^[1]

Physical characteristics

In the Tholen taxonomic scheme, Clemence is classified as an X-type asteroid.^[1] It has also been characterized as an E-type asteroid by the NEOWISE mission.^[5]

Rotation period

In March 2005, a rotational lightcurve was obtained by American astronomer Brian Warner at his Palmer Divide Observatory (716) in Colorado. Lightcurve analysis gave a rotation period of 67.4±0.1 hours and a brightness variation of 0.15 magnitude (U=2, revised analysis).^[7] While not being a slow rotator, Clemence has a significantly longer period than most other asteroids, which typically have a spin rate between 2 and 20 hours.

Czech astronomer Petr Pravec from the Ondřejov Observatory believes this may be a tumbling asteroid, yet observations are not sufficient to determine a non-principal axis rotation.^[8][9]

Diameter and albedo

According to the surveys carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, the asteroid measures 3.2 kilometers in diameter and its surface has an outstandingly high albedo of 0.71,^[5] while the Collaborative Asteroid Lightcurve Link assumes an albedo of 0.30 and calculates a somewhat larger diameter of 4.95 kilometers with an absolute magnitude of 13.45.^[4]

Naming

This minor planet was named after American astronomer Gerald Maurice Clemence (1908–1974), first scientific director of the United States Naval Observatory and professor of astronomy at the Yale Observatory, known for his work on the theory of the motion of Mars and Mercury, on the system of astronomical constants, and other research in celestial mechanics. He served as president of the American Astronomical Society and of IAU.^[2] The official naming citation was published by the Minor Planet Center on 20 February 1976 (M.P.C. 3937).^[10]