1512 Oulu
Hildian asteroid and slow rotator
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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 Alikoski at Turku Observatory in Southwest Finland and named for the Finnish town Oulu.[2][12]
Hubble Space Telescope image of Oulu taken in 2012 | |
| Discovery[1] | |
|---|---|
| Discovered by | H. Alikoski |
| Discovery site | Turku Obs. |
| Discovery date | 18 March 1939 |
| Designations | |
| (1512) Oulu | |
Named after | Oulu (Finnish town)[2] |
| 1939 FE · 1938 CU 1957 TA · 1958 XS | |
| main-belt · Hilda[3] | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 78.06 yr (28,510 days) |
| Aphelion | 4.5541 AU |
| Perihelion | 3.3892 AU |
| 3.9717 AU | |
| Eccentricity | 0.1466 |
| 7.92 yr (2,891 days) | |
| 333.83° | |
| 0° 7m 28.2s / day | |
| Inclination | 6.4785° |
| 10.168° | |
| 238.20° | |
| Jupiter MOID | 0.6287 AU |
| Physical characteristics | |
| Dimensions | 65.0 km[4] 65.000±4.137 km[5] 79.222±0.241 km[6] 82.72±2.5 km (IRAS:38)[7] 91.05±2.20 km[8] |
| 132.3±0.1 h[9] | |
| 0.031±0.001[8] 0.0366±0.002 (IRAS:38)[7] 0.038±0.005[6] 0.0536±0.0061[5] 0.0594[4] 0.06±0.03[10] | |
| Tholen = P[1] · X[11] · P[3] BâV = 0.715[1] UâB = 0.190[1] | |
| 9.62[1][3][5][4][7][8] · 9.92±0.40[11] | |
Orbit and classification
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.
Oulu orbits the Sun at a distance of 3.4â4.6 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 CU at Bergedorf Observatory. Its observation arc, however, begins one month after its official discovery observation.[12]
Physical characteristics
Oulu is characterized as a dark and reddish P-type asteroid in the Tholen taxonomy, of which only a few dozen bodies are currently known.[13]
Slow rotator and likely tumbler
In May 2009, a rotational light curve of Oulu was obtained from photometric observations by Slovak astronomer Adrián Galád at Modra Observatory. Lightcurve analysis gave a rotation period of 132.3 hours with a brightness variation of 0.33 in magnitude (U=2+).[9] It is among the top few hundred slow rotators.
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]
Diameter and albedo
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 occultation by Oulu, that gave a diameter of 65.0 kilometers with an occultation albedo of 0.0594.[4]
Naming
This minor planet was named for the northern Finnish town Oulu, the birthplace of the discoverer.[2] The official naming citation was published by the Minor Planet Center on 30 January 1964 (M.P.C. 2278).[15]
