Discovered by Y. Väisälä MPC designation 1521 Seinajoki Discovered 22 October 1938 Orbits Sun Discovery site Iso-Heikkilä Observatory | Discovery date 22 October 1938 Minor planet category main-belt · (outer) Absolute magnitude 11.5 Discoverer Yrjö Väisälä Asteroid group Asteroid belt | |
Alternative names 1938 UB1 · 1933 UR11967 UW Similar 1450 Raimonda, Solar System, Sun | ||
1521 Seinäjoki, provisional designation 1938 UB1, is an asteroid from the outer region of the asteroid belt, approximately 14 kilometers in diameter. It was discovered by Finnish astronomer Yrjö Väisälä at the southwestern Turku Observatory, Finland, on 22 October 1938.
Seinäjoki orbits the Sun at a distance of 2.5–3.2 AU once every 4 years and 10 months (1,759 days). Its orbit has an eccentricity of 0.14 and an inclination of 15° with respect to the ecliptic. In 1933, Seinäjoki was first identified as 1933 UR1 at Simeiz Observatory. The body's observation arc, however, begins with its official discovery observation at Turku.
In October 2010, a rotational light-curve of Seinäjoki was obtained by Russell Durkee at the U.S. Shed of Science Observatory (H39) in Minneapolis. It gave it a well-defined rotation period of 4.32 hours with a brightness variation of 0.15 magnitude (U=3). A modeled light-curve form Lowell photometric database gave a concurring period of 4.328 hours and a spin axis of (-18.0°, 230.0°) in ecliptic coordinates.
According to the survey carried out by NASA's Wide-field Infrared Survey Explorer (WISE) with its subsequent NEOWISE mission, Seinäjoki measures between 13.66 and 14.81 kilometers in diameter, and its surface has an albedo between 0.205 and 0.22 (more recent results only). The Collaborative Asteroid Lightcurve Link assumes a standard albedo for carbonaceous C-type asteroids of 0.057 and calculates a much larger diameter of 24.30 kilometers as a body's and diameter and reflectivity (albeo) correlate indirectly. However, based on the much higher albedo given by WISE/NEOWISE, the body is rather of a stony composition, which is untypical for asteroids in the outer main-belt.
This minor planet was named for the city of Seinäjoki, located in Southern Ostrobothnia, western Finland. Naming citation was published before November 1977 (M.P.C. 3929).