1523 Pieksämäki

1523 Pieksämäki, provisional designation 1939 BC, is a stony Florian asteroid from the inner regions of the asteroid belt, approximately 9 kilometers in diameter. It was discovered on 18 January 1939, by Finnish astronomer Yrjö Väisälä at the Turku Observatory in Southwest Finland, and named for the town of Pieksämäki.^[2][12]

1523 Pieksämäki

Discovery[1]
Discovered by	Y. Väisälä
Discovery site	Turku Obs.
Discovery date	18 January 1939
Designations
MPC designation	(1523) Pieksamaki
Named after	Pieksämäki (Finnish town)[2]
Alternative designations	1939 BC · 1936 FO1 1936 HC · 1946 GB 1949 AC
Minor planet category	main-belt · Flora[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	80.20 yr (29,294 days)
Aphelion	2.4509 AU
Perihelion	2.0327 AU
Semi-major axis	2.2418 AU
Eccentricity	0.0933
Orbital period (sidereal)	3.36 yr (1,226 days)
Mean anomaly	131.04°
Inclination	5.1411°
Longitude of ascending node	327.79°
Argument of perihelion	187.58°
Physical characteristics
Dimensions	8.98 km (calculated)[3] 9.111±0.313 km[4] 10.008±0.057 km[5]
Synodic rotation period	5.3202±0.0005 h[6][7] 5.3210±0.0001 h[8] 5.33 h[9]
Geometric albedo	0.2135±0.0277[5] 0.24 (assumed)[3] 0.281±0.041[10] 0.505±0.294[4]
Spectral type	S[3]
Absolute magnitude (H)	11.56[4] · 12.3[5] · 12.4[1][3] · 12.58±0.53[11]

Orbit and classification

This S-type asteroid is a member of the Flora family, one of the largest groups of stony asteroids in the main-belt. It orbits the Sun at a distance of 2.0–2.5 AU once every 3 years and 4 months (1,226 days). Its orbit has an eccentricity of 0.09 and an inclination of 5° with respect to the ecliptic.^[1] In 1936, it was first identified as 1936 FO₁ at Nice Observatory, extending Pieksämäki's observation arc by 3 years prior to its official discovery observation at Turku.^[12]

Physical characteristics

Lightcurves

In December 2005, American amateur astronomer Donald P. Pray obtained a rotational lightcurve at Carbuncle Hill Observatory in collaboration with other astronomers. Light-curve analysis gave a well-defined rotation period of 5.3202 hours with a brightness variation of 0.47 magnitude (U=3).^[6]

Previous photometric observations were made by Kryszczyńska et al. in July 2004, that gave an identical period with an amplitude of 0.40 magnitude (U=2+),^[7] and by Claes-Ingvar Lagerkvist, who derived a period of 5.33 hours (Δ0.5 mag) already in the 1970s (U=2).^[9] In March 2013, another well-defined period of 5.3210 hours (Δ0.42 mag) was obtained by French amateur astronomer René Roy.^[8]

Diameter and albedo

According to the surveys carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Pieksämäki measures 9.111 and 10.008 kilometers in diameter, and its surface has an albedo between 0.213 and 0.505.^[4][5][10] The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.24 – derived from 8 Flora, the family's principal body and namesake – and calculates a diameter of 8.98 kilometers based on an absolute magnitude of 12.4.^[3]

Naming

This minor planet was named for Pieksämäki, an eastern Finnish town in Southern Savonia.^[2] The official naming citation was published by the Minor Planet Center on 20 February 1976 (M.P.C. 3929).^[13]