1521 Seinäjoki

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1521 Seinäjoki
Discovery [1]
Discovered byY. Väisälä
Discovery siteTurku Obs.
Discovery date22 October 1938
MPC designation(1521) Seinajoki
Named after
Seinäjoki (Finnish city)[2]
1938 UB1 · 1933 UR1
1967 UW
main-belt · (outer)[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc78.62 yr (28,716 days)
Aphelion3.2435 AU
Perihelion2.4633 AU
2.8534 AU
4.82 yr (1,760 days)
0° 12m 16.2s / day
Physical characteristics
Dimensions13.66±3.61 km[5]
14.813±0.070 km[6]
16.095±0.070 km[7]
16.29±0.20 km[8]
24.30 km (calculated)[3]
4.32±0.01 h[9]
4.328159±0.000001 h[10]
0.057 (assumed)[3]
11.5[7] · 11.8[1][3] · 11.90[8] · 11.92[5] · 12.17±0.45[11]

1521 Seinäjoki, provisional designation 1938 UB1, is a Brasilia asteroid from the outer region of the asteroid belt, approximately 14 kilometers in diameter.

It was discovered on 22 October 1938, by Finnish astronomer Yrjö Väisälä at the southwestern Turku Observatory, Finland.[12] The asteroid was later named after the Finnish city of Seinäjoki.[2]

Orbit and classification[edit]

Seinäjoki is a member of the Brasilia family, a smaller asteroid family of X-type asteroids in the outer main-belt. Since the family's namesake, 293 Brasilia, is a suspected interloper in its own family, it has also been named Seinäjoki family after Seinäjoki.[4][13]:37

It orbits the Sun in the outer main-belt at a distance of 2.5–3.2 AU once every 4 years and 10 months (1,760 days). Its orbit has an eccentricity of 0.14 and an inclination of 15° with respect to the ecliptic.[1] 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.[12]

Physical characteristics[edit]

Rotation and pole[edit]

In October 2010, a rotational lightcurve 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).[9] A modeled lightcurve form Lowell photometric database gave a concurring period of 4.328 hours and a spin axis of (-18.0°, 230.0°) in ecliptic coordinates.[10]

Diameter and albedo[edit]

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).[5][6][7][8]

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.[3] 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.[2] The official naming citation was published before November 1977 (M.P.C. 3929).[14]


  1. ^ a b c d "JPL Small-Body Database Browser: 1521 Seinajoki (1938 UB1)" (2017-06-05 last obs.). Jet Propulsion Laboratory. Retrieved 30 June 2017.
  2. ^ a b c Schmadel, Lutz D. (2007). "(1521) Seinäjoki". Dictionary of Minor Planet Names – (1521) Seinäjoki. Springer Berlin Heidelberg. p. 121. doi:10.1007/978-3-540-29925-7_1522. ISBN 978-3-540-00238-3. Retrieved 3 January 2017.
  3. ^ a b c d e f "LCDB Data for (1521) Seinäjoki". Asteroid Lightcurve Database (LCDB). Retrieved 3 January 2017.
  4. ^ a b "Small Bodies Data Ferret". Nesvorny HCM Asteroid Families V3.0. Retrieved 2 September 2017.
  5. ^ a b c d Nugent, C. R.; Mainzer, A.; Bauer, J.; Cutri, R. M.; Kramer, E. A.; Grav, T.; et al. (September 2016). "NEOWISE Reactivation Mission Year Two: Asteroid Diameters and Albedos". The Astronomical Journal. 152 (3): 12. arXiv:1606.08923. Bibcode:2016AJ....152...63N. doi:10.3847/0004-6256/152/3/63. Retrieved 3 January 2017.
  6. ^ a b c Masiero, Joseph R.; Grav, T.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; et al. (August 2014). "Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos". The Astrophysical Journal. 791 (2): 11. arXiv:1406.6645. Bibcode:2014ApJ...791..121M. doi:10.1088/0004-637X/791/2/121. Retrieved 3 January 2017.
  7. ^ 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" (PDF). The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90. Retrieved 3 January 2017.
  8. ^ a b c d Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Nugent, C.; et al. (November 2012). "Preliminary Analysis of WISE/NEOWISE 3-Band Cryogenic and Post-cryogenic Observations of Main Belt Asteroids". The Astrophysical Journal Letters. 759 (1): 5. arXiv:1209.5794. Bibcode:2012ApJ...759L...8M. doi:10.1088/2041-8205/759/1/L8. Retrieved 3 January 2017.
  9. ^ a b Durkee, Russell I. (January 2011). "Asteroids Observed from the Shed of Science Observatory: 2010 May-October". The Minor Planet Bulletin. 38 (1): 39–40. Bibcode:2011MPBu...38...39D. ISSN 1052-8091. Retrieved 3 January 2017.
  10. ^ a b Durech, J.; Hanus, J.; Oszkiewicz, D.; Vanco, R. (March 2016). "Asteroid models from the Lowell photometric database". Astronomy and Astrophysics. 587: 6. arXiv:1601.02909. Bibcode:2016A&A...587A..48D. doi:10.1051/0004-6361/201527573. Retrieved 3 January 2017.
  11. ^ 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 3 January 2017.
  12. ^ a b "1521 Seinajoki (1938 UB1)". Minor Planet Center. Retrieved 3 January 2017.
  13. ^ Nesvorný, D.; Broz, M.; Carruba, V. (December 2014). "Identification and Dynamical Properties of Asteroid Families" (PDF). Asteroids IV: 297–321. arXiv:1502.01628. Bibcode:2015aste.book..297N. doi:10.2458/azu_uapress_9780816532131-ch016. Retrieved 2 September 2017.
  14. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 3 January 2017.

External links[edit]