1573 Väisälä, provisional designation 1949 UA, is a stony Phocaea asteroid, slow rotator and suspected tumbler from the inner regions of the asteroid belt, approximately 9 kilometers in diameter. It was discovered on 27 October 1949, by Belgian astronomer Sylvain Arend at the Royal Observatory of Belgium in Uccle, Belgium.[11] It was named for Finnish astronomer Yrjö Väisälä.[2]
Orbit and classification
The stony S-type asteroid is a member of the Phocaea family (701), a group of asteroids with similar orbital characteristics.[4] It orbits the Sun at a distance of 1.8–2.9 AU once every 3 years and 8 months (1,334 days). Its orbit has an eccentricity of 0.23 and an inclination of 25° with respect to the ecliptic.[1]Väisälä's observation arc begins on the night following its official discovery observation at Uccle, as no precoveries were taken and no prior identifications were made.[11]
Physical characteristics
Slow rotator
In September 2011, a rotational lightcurve of Väisälä was obtained from photometric observations made by Czech astronomer Petr Pravec at Ondřejov Observatory.[b] Its analysis gave a rotation period of 252 hours with a brightness variation of 0.76 magnitude (U=2).[a] This makes Väisälä one of the Top 200 slow rotators known to exist. The body is also suspected to be in a non-principal axis rotation (NPAR), colloquially called as "tumbling". As of 2017, no follow-up observations have been made of these provisional results.[3]
Diameter and albedo
According to the space-based surveys carried out by the Infrared Astronomical Satellite IRAS, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Väisälä measures between 8.43 and 9.77 kilometers in diameter, and its surface has an albedo between 0.222 and 0.284.[5][6][7][8] The Collaborative Asteroid Lightcurve Link adopts the results obtained by IRAS, that is, an albedo of 0.2226 and a diameter of 9.77 kilometers using on an absolute magnitude of 12.30.[3]