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1542 Schalén
	Shape model of Schalén from its lightcurve
Discovery
Discovered by	Y. Väisälä
Discovery site	Turku Obs.
Discovery date	26 August 1941
Designations
MPC designation	(1542) Schalén
Named after	Karl Schalén (astronomer)
Alternative designations	1941 QE · 1927 BH; 1936 UL · 1940 LP; 1976 CA · A898 VD; A924 NA
Minor planet category	main-belt · background
Orbital characteristics
	Epoch 16 February 2017 (JD 2457800.5)
	Uncertainty parameter 0
Observation arc	117.73 yr (43,001 days)
Aphelion	3.4510 AU
Perihelion	2.7343 AU
Semi-major axis	3.0926 AU
Eccentricity	0.1159
Orbital period (sidereal)	5.44 yr (1,987 days)
Mean anomaly	284.94°
Mean motion	0° 10m 52.32s / day
Inclination	2.7662°
Longitude of ascending node	211.66°
Physical characteristics
Dimensions	42.374±0.273 km; 45.05 km (derived); 48.998±0.480 km
Synodic rotation period	7.516±0.002 h
Geometric albedo	0.0501 (derived); 0.0509±0.0105; 0.068±0.003
Spectral type	SMASS = D
Absolute magnitude (H)	10.4 · 10.6

1542 Schalén, provisional designation 1941 QE, is a background asteroid from the outer region of the asteroid belt, approximately 45 kilometers in diameter. It was discovered on 26 August 1941, by Finnish astronomer Yrjö Väisälä at Turku Observatory in Southwest Finland.^[7] The dark D-type asteroid was later named after Swedish astronomer Karl Schalén.^[2]

Orbit and classification

Schalén is a background asteroid, located near the region of the Themis family, a dynamical family of outer-belt asteroids with nearly coplanar ecliptical orbits.^[3] It orbits the Sun at a distance of 2.7–3.5 AU once every 5 years and 5 months (1,987 days). Its orbit has an eccentricity of 0.12 and an inclination of 3° with respect to the ecliptic.^[1] It was first identified as A898 VD at Heidelberg Observatory in 1898, extending the body's observation arc by 43 years prior to its official discovery observation at Turku.^[7]

Physical characteristics

Schalén has a dark D-type spectrum, mostly found among Hildian asteroids and Jupiter trojans.^[8] Bodies with a D-type spectra are thought to have originated in the Kuiper belt.

Diameter and albedo

According to the 2014-result of the survey carried by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Schalén measures 42.374 kilometers in diameter and its surface has an albedo of 0.068,^[4] while the Collaborative Asteroid Lightcurve Link derives an albedo of 0.0509 and a diameter of 45.05 kilometers with an absolute magnitude of 10.6.^[3]

Rotation period

In November 2012, a rotational lightcurve of Schalén was obtained from photometric observations by astronomers at the Purple Mountain Observatory in collaboration with observatories in the United States. Lightcurve analysis gave a well-defined rotation period of 7.516 hours with a brightness variation of 0.49 magnitude (U=3).^[6]

Naming

This minor planet was named in honour of Swedish astronomer Karl Adam Wilhelm Schalén (1902–1993), who was a director of the Swedish Lund Observatory.^[2] The official naming citation was published by the Minor Planet Center on 20 February 1976 (M.P.C. 3930).^[9]

References

^ ^a ^b ^c ^d ^e "JPL Small-Body Database Browser: 1542 Schalen (1941 QE)" (2016-08-08 last obs.). Jet Propulsion Laboratory. Retrieved 30 December 2016.
^ ^a ^b ^c Schmadel, Lutz D. (2007). "(1542) Schalén". Dictionary of Minor Planet Names – (1542) Schalén. Springer Berlin Heidelberg. p. 122. doi:10.1007/978-3-540-29925-7_1543. ISBN 978-3-540-00238-3.
^ ^a ^b ^c ^d ^e ^f ^g "LCDB Data for (1542) Schalén". Asteroid Lightcurve Database (LCDB). Retrieved 30 December 2016.
^ ^a ^b ^c Masiero, Joseph R.; Grav, T.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; et al. (August 2014). "Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos". The Astrophysical Journal. 791 (2): 11. arXiv:1406.6645. Bibcode:2014ApJ...791..121M. doi:10.1088/0004-637X/791/2/121. Retrieved 30 December 2016.
^ ^a ^b ^c Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90.
^ ^a ^b Li, Bin; Zhao, Haibin; Han, Xianming L.; Klinglesmith, Daniel A. III; Hanowell, Jesse (April 2013). "Photometric Observation of 1542 Schalen". The Minor Planet Bulletin. 40 (2): 68–69. Bibcode:2013MPBu...40...68L. ISSN 1052-8091. Retrieved 30 December 2016.
^ ^a ^b "1542 Schalen (1941 QE)". Minor Planet Center. Retrieved 30 December 2016.
^ "JPL Small-Body Database Search Engine: [ spec. type = D (Tholen) or spec. type = D (SMASSII) ]". JPL Solar System Dynamics. Retrieved 30 December 2016.
^ Schmadel, Lutz D. "Appendix – Publication Dates of the MPCs". Dictionary of Minor Planet Names – Addendum to Fifth Edition (2006–2008). Springer Berlin Heidelberg. p. 221. doi:10.1007/978-3-642-01965-4. ISBN 978-3-642-01964-7.