1512 Oulu, provisional designation 1939 FE, is a dark Hildian asteroid, slow rotator and possibly the largest known tumbler orbiting in the outermost region of the asteroid belt. With a diameter of approximately 80 kilometers, it belongs to the fifty largest asteroids in the outer main-belt. The body was discovered on 18 March 1939, by Finnish astronomer Heikki AlikoskiatTurku Observatory in Southwest Finland and named for the Finnish town Oulu.[2][12]
Located in the outermost part of the main-belt, Oulu is a member of the Hilda family, a large orbital group of asteroids that are thought to have originated from the Kuiper belt. They orbit in a 3:2 orbital resonance with the gas giant Jupiter, meaning that for every 2 orbits Jupiter completes around the Sun, a Hildian asteroid will complete 3 orbits.[1] As it does not cross the path of any of the planets, it will not be pulled out of orbit by Jupiter's gravitational field, and will likely remain in a stable orbit for thousands of years.
It orbits the Sun at a distance of 3.4–4.6 AU once every 7 years and 11 months (2,891 days). Its orbit has an eccentricity of 0.15 and an inclination of 6° concerning the ecliptic.[1] In 1938, Oulu was first identified as 1938 CUatBergedorf Observatory. Its observation arc, however, begins one month after its official discovery observation.[12]
Oulu is likely in a state of non-principal axis rotation, which is commonly known as tumbling. It is the largest such object ever observed (also see List of tumblers).[3][9][14]
According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Oulu measures between 65.00 and 91.05 kilometers in diameter, and its surface has an albedo between 0.031 and 0.06.[5][6][7][8][10]
The Collaborative Asteroid Lightcurve Link agrees with IRAS, that is, an albedo of 0.0366 and a diameter of 82.72 kilometers using an absolute magnitude of 9.62.[3] In May 2002, Vasilij Shevchenko and Edward Tedesco observed an occultationbyOulu, that gave a diameter of 65.0 kilometers with an occultation albedo of 0.0594.[4]
^ abcdUsui, Fumihiko; Kuroda, Daisuke; Müller, Thomas G.; Hasegawa, Sunao; Ishiguro, Masateru; Ootsubo, Takafumi; et al. (October 2011). "Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey". Publications of the Astronomical Society of Japan. 63 (5): 1117–1138. Bibcode:2011PASJ...63.1117U. doi:10.1093/pasj/63.5.1117. (online, AcuA catalog p. 153)
