2004 Lexell

2004 Lexell, provisional designation 1973 SV₂, is a stony Florian asteroid from the inner regions of the asteroid belt, approximately 7.5 kilometers in diameter. The asteroid was discovered on 22 September 1973, by Soviet astronomer Nikolai Chernykh at the Crimean Astrophysical Observatory in Nauchnij, on the Crimean peninsula, and later named for Swedish-Russian astronomer and mathematician Anders Johan Lexell.^[2][10]

2004 Lexell

Discovery[1]
Discovered by	N. Chernykh
Discovery site	Crimean Astrophysical Obs.
Discovery date	22 September 1973
Designations
MPC designation	(2004) Lexell
Named after	Anders Johan Lexell (Swedish-Russian astronomer)[2]
Alternative designations	1973 SV2 · 1938 WL 1941 SN1 · 1959 GC 1972 HK
Minor planet category	main-belt · Flora[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	78.55 yr (28,689 days)
Aphelion	2.3451 AU
Perihelion	1.9986 AU
Semi-major axis	2.1718 AU
Eccentricity	0.0798
Orbital period (sidereal)	3.20 yr (1,169 days)
Mean anomaly	215.94°
Mean motion	0° 18m 28.44s / day
Inclination	2.4967°
Longitude of ascending node	4.5440°
Argument of perihelion	58.504°
Physical characteristics
Dimensions	7.255±0.216 km[4] 7.456±0.084 km[5] 7.82 km (calculated)[3] 14.7 km[6]
Synodic rotation period	5.44±0.02 h[7] 5.441±0.002 h[8] 5.4429±0.0003 h[6]
Geometric albedo	0.056[6] 0.24 (assumed)[3] 0.2908±0.0522[5] 0.306±0.041[4]
Spectral type	LS[9] · S[3]
Absolute magnitude (H)	12.6[5] · 12.7[1][3] · 12.908±0.064[6] · 13.04±0.00[9]

Classification and orbit

Lexell is a member of the Flora family, one of the largest collisional populations of stony asteroids. It orbits the Sun at a distance of 2.0–2.3 AU once every 3 years and 2 months (1,169 days). Its orbit has an eccentricity of 0.08 and an inclination of 2° with respect to the ecliptic.^[1]

The asteroid was first identified as 1938 WL at the Finnish Turku Observatory in November 1938, extending the body's observation arc by 35 years prior to its official discovery observation at Nauchnij.^[10]

Physical characteristics

Pan-STARRS' photometric survey characterized Lexell as a LS-type asteroid, which transitions between the common S-type and rare L-type asteroid.^[9]

Rotation period

In March 2013, two rotational lightcurves of Lexell were obtained from photometric observations by Gary Haagen at Stonegate Observatory, Massachusetts, and by a group of astronomers at the Oakley Southern Sky Observatory (E09), Australia. Lightcurve analysis gave a well-defined rotation period of 5.441 and 5.4429 hours with a brightness variation of 0.45 and 0.42 magnitude, respectively (U=3/3).^[6][8]

In February 2013, observations made by French amateur astronomer Pierre Antonini gave a concurring period of 5.44 hours with an amplitude of 0.51 magnitude (U=3-).^[7]

Diameter and albedo

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Lexell measures 7.255 and 7.456 kilometers in diameter and its surface has an albedo of 0.306 and 0.2908, respectively.^[4][5] The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.24 – derived from 8 Flora, the largest member and namesake of the Flora family – and calculates a diameter of 7.82 kilometers based on an absolute magnitude of 12.7.^[3]

Naming

This minor planet was named after Anders Johan Lexell (1740–1784), a Swedish-Russian astronomer and mathematician. The official naming citation was published by the Minor Planet Center on 15 October 1977 (M.P.C. 4238).^[11] The lunar crater Lexell was also named in his honor, as is Lexell's Comet, of which he computed its orbit.^[2]