1928 Summa

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1928 Summa
Discovery [1]
Discovered by Y. Väisälä
Discovery site Turku Obs.
Discovery date 21 September 1938
MPC designation (1928) Summa
Named after
Finnish village
(Battle of Summa)[2]
1938 SO · 1969 PA
main-belt · (inner)[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc 78.38 yr (28,628 days)
Aphelion 2.9797 AU
Perihelion 1.9733 AU
2.4765 AU
Eccentricity 0.2032
3.90 yr (1,423 days)
0° 15m 10.44s / day
Inclination 4.5756°
Physical characteristics
Dimensions 8.34 km (derived)[3]
9.333±0.170 km[4][5]
6.8549±0.0006 h[6]
6.855±0.001 h[7]
9.66 h (dated)[8]
0.20 (assumed)[3]
B–V = 1.010[1]
12.68[1] · 12.76[3][4][8] · 13.20±0.85[9]

1928 Summa, provisional designation 1938 SO, is a stony asteroid from the inner regions of the asteroid belt, approximately 9 kilometers in diameter.

It was discovered on 21 September 1938, by Finnish astronomer Yrjö Väisälä at Turku Observatory in Southwest Finland.[10] It was named for a Finnish village where the Battle of Summa took place.[2]

Orbit and classification[edit]

Summa is a S-type asteroid that orbits the Sun in the inner main-belt at a distance of 2.0–3.0 AU once every 3 years and 11 months (1,423 days). Its orbit has an eccentricity of 0.20 and an inclination of 5° with respect to the ecliptic.[1] The body's observation arc begins at Turku one night after its official discovery observation, with no precoveries taken, and no prior identifications made.[10]

Rotation period[edit]

In March 1984, the first but poorly rated rotational lightcurve of Summa was obtained from photometric observations by American astronomer Richard Binzel. It gave a rotation period of 9.66 hours with a brightness amplitude of 0.14 magnitude (U=1).[8]

In August 2012, a refined yet ambiguous lightcurve with a period of 6.855 hours and an amplitude of 0.13 was obtained by Larry E. Owings at the Barnes Ridge Observatory in California (U=2+). Lightcurve analysis also considered that Summa might be a binary system.[7] One month later, the so-far best rated lightcurve from British astronomer Kevin Hills using the remote controlled Riverland Dingo Observatory in Australia, gave a period of 6.8549 hours with a brightness amplitude of 0.18 (U=3).[6]

Diameter an albedo[edit]

According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Summa measures 9.333 kilometers in diameter and its surface has an albedo of 0.160,[4][5] while the Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 8.34 kilometers with an absolute magnitude of 12.76.[3]


This minor planet was named after the village on the Karelian Isthmus, where the Battle of Summa took place during the Finnish Winter War (1939–1940).[2] The approved naming citation was published by the Minor Planet Center on 1 August 1980 (M.P.C. 5450).[11] Most of Yrjö Väisälä's discoveries have names that relate in one way or another to this military conflict between Finland and the Soviet Union during World War II.


  1. ^ a b c d e "JPL Small-Body Database Browser: 1928 Summa (1938 SO)" (2017-02-08 last obs.). Jet Propulsion Laboratory. Retrieved 2 July 2017. 
  2. ^ a b c Schmadel, Lutz D. (2007). Dictionary of Minor Planet Names – (1928) Summa. Springer Berlin Heidelberg. p. 155. ISBN 978-3-540-00238-3. Retrieved 5 April 2017. 
  3. ^ a b c d e f "LCDB Data for (1928) Summa". Asteroid Lightcurve Database (LCDB). Retrieved 5 April 2017. 
  4. ^ 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:1109.6407Freely accessible. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90. Retrieved 5 April 2017. 
  5. ^ a b c Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Dailey, J.; et al. (November 2011). "Main Belt Asteroids with WISE/NEOWISE. I. Preliminary Albedos and Diameters". The Astrophysical Journal. 741 (2): 20. arXiv:1109.4096Freely accessible. Bibcode:2011ApJ...741...68M. doi:10.1088/0004-637X/741/2/68. Retrieved 5 April 2017. 
  6. ^ a b Hills, Kevin (January 2013). "Asteroid Lightcurve Analysis at Riverland Dingo Observatory (RDO): 501 Urhixidur, 1897 Hind, 1928 Summa, 6261 Chione, and (68216) 2001 CV 26". The Minor Planet Bulletin. 40 (1): 12–13. Bibcode:2013MPBu...40...12H. ISSN 1052-8091. Retrieved 5 April 2017. 
  7. ^ a b Owings, Larry E. (April 2013). "Lightcurves for 1560 Strattonia, 1928 Summa, 2763 Jeans, 3478 Fanale, 3948 Bohr, 5275 Zdislava, and 5369 Virgiugum". The Minor Planet Bulletin. 40 (2): 104–106. Bibcode:2013MPBu...40..104O. ISSN 1052-8091. Retrieved 5 April 2017. 
  8. ^ a b c d Binzel, R. P. (October 1987). "A photoelectric survey of 130 asteroids". Icarus: 135–208. Bibcode:1987Icar...72..135B. doi:10.1016/0019-1035(87)90125-4. ISSN 0019-1035. Retrieved 5 April 2017. 
  9. ^ 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:1506.00762Freely accessible. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. Retrieved 5 April 2017. 
  10. ^ a b "1928 Summa (1938 SO)". Minor Planet Center. Retrieved 5 April 2017. 
  11. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 5 April 2017. 

External links[edit]