1496 Turku

1496 Turku, provisional designation 1938 SA₁, is a Florian asteroid from the inner regions of the asteroid belt, approximately 8 kilometers in diameter. It was discovered on 22 September 1938, by astronomer Yrjö Väisälä at the Iso-Heikkilä Observatory in Turku, Finland.^[11] The asteroid was named for the Finnish city of Turku.^[2]

1496 Turku

Shape of Turku modelled from its lightcurve
Discovery[1]
Discovered by	Y. Väisälä
Discovery site	Turku Obs.
Discovery date	22 September 1938
Designations
MPC designation	(1496) Turku
Named after	Turku[2] (Finnish city)
Alternative designations	1938 SA1 · 1928 QN 1928 RE · 1950 EC 1954 MH · 1957 HB
Minor planet category	main-belt · (inner) Flora[3] · background[4]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc	88.02 yr (32,148 days)
Aphelion	2.5631 AU
Perihelion	1.8490 AU
Semi-major axis	2.2060 AU
Eccentricity	0.1619
Orbital period (sidereal)	3.28 yr (1,197 days)
Mean anomaly	90.547°
Mean motion	0° 18m 2.88s / day
Inclination	2.5005°
Longitude of ascending node	294.38°
Argument of perihelion	0.9272°
Physical characteristics
Dimensions	7.47±0.31 km[5] 7.758±0.072 km[6] 7.973±0.018 km[7] 8.19 km (calculated)[3]
Synodic rotation period	6.47±0.01 h[8] 6.47375±0.00001 h[9]
Geometric albedo	0.1930±0.0196[7] 0.203±0.024[6] 0.24 (assumed)[3] 0.347±0.043[5]
Spectral type	S (assumed)[3]
Absolute magnitude (H)	12.40[5] · 12.42±0.25[10] · 12.6[1][3] · 12.9[7]

Orbit and classification

Turku is a member of the Flora family (402), a giant asteroid family and the largest family of stony asteroids in the main belt.^[3] It is, however, a non-family asteroid from the main belt's background population when applying the Hierarchical Clustering Method to its proper orbital elements.^[4]

It orbits the Sun in the inner main-belt at a distance of 1.8–2.6 AU once every 3 years and 3 months (1,197 days). Its orbit has an eccentricity of 0.16 and an inclination of 3° with respect to the ecliptic.^[1] The body's observation arc begins with its first identification as 1928 QN at Johannesburg Observatory in August 1928, more than 10 years prior to its official discovery observation at Turku.^[11]

Physical characteristics

Turku is an assumed S-type asteroid, which is also the Flora family's overall spectral type.^[3]

Rotation period and poles

In April 2006, a rotational lightcurve of Turku was obtained from photometric observations by French amateur astronomer Laurent Bernasconi. Lightcurve analysis gave a rotation period of 6.47 hours with a brightness amplitude of 0.51 magnitude, indicative of a non-spherical shape (U=3-).^[8]

A 2016-published lightcurve, using modeled photometric data from the Lowell Photometric Database, gave a concurring period of 6.47375 hours, as well as a spin axis of (75.0°, −75.0°) in ecliptic coordinates (λ, β).^[9]

Diameter and albedo

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Turku measures between 7.47 and 7.973 kilometers in diameter and its surface has an albedo between 0.1930 and 0.347.^[5][6][7]

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 8.19 kilometers based on an absolute magnitude of 12.6.^[3]

Naming

This minor planet was named after Finnish city of Turku, location of the discovering observatory and home of the discoverer Yrjö Väisälä. In ancient times, Turku was the capital of Finland.^[2] The official naming citation was published by the Minor Planet Center in January 1956 (M.P.C. 1350).^[12]