2114 Wallenquist

2114 Wallenquist, provisional designation 1976 HA, is a Themistian asteroid from the outer region of the asteroid belt, approximately 28 kilometers in diameter. It was discovered by Swedish astronomer Claes-Ingvar Lagerkvist at the Australian Mount Stromlo Observatory near Canberra, on 19 April 1976.^[12]

2114 Wallenquist

Discovery[1]
Discovered by	C.-I. Lagerkvist
Discovery site	Mount Stromlo Obs.
Discovery date	19 April 1976
Designations
MPC designation	(2114) Wallenquist
Named after	Åke Wallenquist (Swedish astronomer)[2]
Alternative designations	1976 HA · 1930 DG 1942 LD · 1953 GZ 1964 FA · 1970 EO3 1970 EZ2
Minor planet category	main-belt · Themis[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	63.51 yr (23,198 days)
Aphelion	3.6508 AU
Perihelion	2.7467 AU
Semi-major axis	3.1987 AU
Eccentricity	0.1413
Orbital period (sidereal)	5.72 yr (2,090 days)
Mean anomaly	91.271°
Mean motion	0° 10m 20.28s / day
Inclination	0.5558°
Longitude of ascending node	1.5530°
Argument of perihelion	216.98°
Physical characteristics
Dimensions	21.12±1.26 km[4] 22.558±0.079[5] 23.008±0.190 km[6] 27.45 km (derived)[3] 27.67±2.3 km (IRAS:2)[7]
Synodic rotation period	5.49±0.01 h[8] 5.5078±0.0009 h[9] 5.510±0.005 h[10]
Geometric albedo	0.0447 (derived)[3] 0.0838±0.016 (IRAS:2)[7] 0.1216±0.0099[6] 0.145±0.019[5] 0.149±0.020[4]
Spectral type	S[3]
Absolute magnitude (H)	11.1[7][4][6] · 11.749±0.002 (R)[9] · 11.8[1][3] · 11.87±0.23[11]

Orbit and classification

Wallenquist is a member of the Themis family, a dynamical family of outer-belt asteroids with nearly coplanar ecliptical orbits. It orbits the Sun in the outer main-belt at a distance of 2.7–3.7 AU once every 5 years and 9 months (2,090 days). Its orbit has an eccentricity of 0.14 and an inclination of 1° with respect to the ecliptic.^[1] The first used observation was made at the U.S. Goethe Link Observatory in 1953, extending the asteroid's observation arc by 23 years prior to its discovery.^[12]

Physical characteristics

Rotation period

In April 2010, a rotational lightcurve of Wallenquist obtained by American astronomer Robert Stephens at the Goat Mountain Astronomical Research Station (GMARS, G79), California, gave a well-defined rotation period of 5.510 hours with a brightness amplitude of 0.22 magnitude (U=3).^[10]

Two other observations, by French astronomer René Roy at Blauvac Observatory (627), France, and by astronomers at the U.S. Palomar Transient Factory, gave a period of 5.49±0.01 and 5.5078±0.0009, with an amplitude of 0.30 and 0.23, respectively (U=2/2).^[8][9]

Diameter and albedo

According to the surveys carried out by the Infrared Astronomical Satellite, IRAS, the Japanese Akari satellite, and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Wallenquist measures between 21.1 and 27.6 kilometers in diameter while its surface has an albedo in the range of 0.08 and 0.15.^[4][5][6][7]

The Collaborative Asteroid Lightcurve Link (CALL) derives an even lower albedo of 0.04 and calculates a diameter of 27.5 kilometer. Despite its low albedo, CALL characterizes the body as a S-type rather than a darker C-type asteroid.^[3]

Naming

This minor planet was named in honor of Swedish astronomer Åke Wallenquist (1904–1994), former director of the Kvistaberg Station, after which the minor planet 3331 Kvistaberg is named.^[2]

After his retirement Wallenquist continued to research dark matter in open clusters at the Uppsala Astronomical Observatory. He co-discovered the near-Earth Amor asteroid 1980 Tezcatlipoca during his stay at the Palomar Observatory in California in 1950.^[2] The official naming citation was published by the Minor Planet Center on 1 February 1979 (M.P.C. 4645).^[13]