Discovered by Y. Väisälä MPC designation 1446 Sillanpaa Observation arc 78.53 yr (28,683 days) Orbits Sun Asteroid family Flora family | Discovery date 26 January 1938 Minor planet category main-belt · Flora Discovered 26 January 1938 Discoverer Yrjö Väisälä Discovery site Iso-Heikkilä Observatory | |
Alternative names 1938 BA · 1935 GB
1952 HQ3 · 1955 DQ
1965 EA Named after Frans Eemil Sillanpää (Writer) Similar 1450 Raimonda, Sun, 8 Flora | ||
1446 Sillanpää, provisional designation 1938 BA, is a stony Florian asteroid from the inner regions of the asteroid belt, approximately 8.2 kilometers in diameter. It was discovered on 26 January 1938, by Finnish astronomer Yrjö Väisälä at Turku Observatory in Southwest Finland.
The S-type asteroid is a member of the Flora family, one of the largest populations 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 (1,229 days). Its orbit has an eccentricity of 0.10 and an inclination of 5° with respect to the ecliptic. Sillanpää was first identified as 1935 GB at Simeiz Observatory in 1935, while its observation arc begins with its official discovery observation at Turku in 1938.
In March 2009, Czech astronomer Petr Pravec obtained a rotational light-curve from photometric observations at Ondřejov Observatory. It gave a well-defined rotation period of 9.6602 hours with a brightness variation of 0.55 magnitude (U=3). One month later, a concurring period of 9.659 hours with an amplitude of 0.71 magnitude was obtained by Adrián Galád at Modra Observatory (U=3). Photometric observations at the Palomar Transient Factory in December 2011. gave a 9.6597 hours and Δ0.59 in magnitude (U=2). A modeled light-curve using data from the Uppsala Asteroid Photometric Catalogue and other data sources, gave a period of 9.65855 hours, as well as a spin axis of (129.0°, 76.0°) in ecliptic coordinates (U=n.a.).
According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Sillanpää measures between 7.35 and 8.76 kilometers in diameter, and its surface has an albedo between 0.21 and 0.327. The Collaborative Asteroid Lightcurve Link assumes an intermediate albedo of 0.24 – derived from 8 Flora, the largest member and namesake of this asteroid family – and calculates a larger diameter of 8.19 kilometers using an absolute magnitude of 12.6.
This minor planet was named after one of the most famous Finnish writers, Frans Eemil Sillanpää (1888–1964), first Finnish writer to receive the Nobel Prize in Literature in 1939 (also see List of Laureates since 1901). Naming citation was published before November 1977 (M.P.C. 3928).