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]

1512 Oulu
1512 Oulu Hubble.jpg
Hubble Space Telescope image of Oulu taken in 2012
Discovered byH. Alikoski
Discovery siteTurku Obs.
Discovery date18 March 1939
(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 arc78.06 yr (28,510 days)
Aphelion4.5541 AU
Perihelion3.3892 AU
3.9717 AU
7.92 yr (2,891 days)
0° 7m 28.2s / day
Jupiter MOID0.6287 AU
Physical characteristics
Dimensions65.0 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]
0.0366±0.002 (IRAS:38)[7]
Tholen = P[1] · X[11] · P[3]
B–V = 0.715[1]
U–B = 0.190[1]
9.62[1][3][5][4][7][8] · 9.92±0.40[11]

Orbit and classificationEdit

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° with respect to 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 characteristicsEdit

Oulu is characterized as a dark and reddish P-type asteroid in the Tholen taxonomy, of which only a few dozens bodies are currently known.[13]

Slow rotator and likely tumblerEdit

In May 2009, a rotational lightcurve 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 albedoEdit

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]


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]


  1. ^ a b c d e f g h "JPL Small-Body Database Browser: 1512 Oulu (1939 FE)" (2017-05-02 last obs.). Jet Propulsion Laboratory. Retrieved 5 June 2017.
  2. ^ a b c Schmadel, Lutz D. (2007). "(1512) Oulu". Dictionary of Minor Planet Names – (1512) Oulu. Springer Berlin Heidelberg. p. 120. doi:10.1007/978-3-540-29925-7_1513. ISBN 978-3-540-00238-3.
  3. ^ a b c d e "LCDB Data for (1512) Oulu". Asteroid Lightcurve Database (LCDB). Retrieved 4 January 2017.
  4. ^ a b c d Shevchenko, Vasilij G.; Tedesco, Edward F. (September 2006). "Asteroid albedos deduced from stellar occultations". Icarus. 184 (1): 211–220. Bibcode:2006Icar..184..211S. doi:10.1016/j.icarus.2006.04.006. Retrieved 4 January 2017.
  5. ^ a b c d Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90.
  6. ^ a b c Grav, T.; Mainzer, A. K.; Bauer, J.; Masiero, J.; Spahr, T.; McMillan, R. S.; et al. (January 2012). "WISE/NEOWISE Observations of the Hilda Population: Preliminary Results". The Astrophysical Journal. 744 (2): 15. arXiv:1110.0283. Bibcode:2012ApJ...744..197G. doi:10.1088/0004-637X/744/2/197. Retrieved 31 December 2016.
  7. ^ a b c d Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System – IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 17 October 2019.
  8. ^ a b c d Usui, 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)
  9. ^ a b c Galad, Adrian; Kornos, Leonard; Vilagi, Jozef (January 2010). "An Ensemble of Lightcurves from Modra". The Minor Planet Bulletin. 37 (1): 9–15. Bibcode:2010MPBu...37....9G. ISSN 1052-8091. Retrieved 4 January 2017.
  10. ^ a b Mainzer, A.; Grav, T.; Masiero, J.; Bauer, J.; Wright, E.; Cutri, R. M.; et al. (August 2011). "Thermal Model Calibration for Minor Planets Observed with Wide-field Infrared Survey Explorer/NEOWISE". The Astrophysical Journal. 736 (2): 9. Bibcode:2011ApJ...736..100M. CiteSeerX doi:10.1088/0004-637X/736/2/100. Retrieved 6 December 2015.
  11. ^ a b Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce; et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 - Preliminary results". Icarus. 261: 34–47. arXiv:1506.00762. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. Retrieved 4 January 2017.
  12. ^ a b "1512 Oulu (1939 FE)". Minor Planet Center. Retrieved 4 January 2017.
  13. ^ "JPL Small-Body Database Search Engine: spec. type = P (Tholen)". JPL Solar System Dynamics. Retrieved 17 June 2015.
  14. ^ Pravec, P.; Scheirich, P.; Durech, J.; Pollock, J.; Kusnirák, P.; Hornoch, K.; et al. (May 2014). "The tumbling spin state of (99942) Apophis". Icarus. 233: 48–60. Bibcode:2014Icar..233...48P. doi:10.1016/j.icarus.2014.01.026. Retrieved 23 November 2017.
  15. ^ Schmadel, Lutz D. (2009). "Appendix – Publication Dates of the MPCs". Dictionary of Minor Planet Names – Addendum to Fifth Edition (2006–2008). Springer Berlin Heidelberg. p. 221. doi:10.1007/978-3-642-01965-4. ISBN 978-3-642-01964-7.

External linksEdit