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1293 Sonja, provisional designation 1933 SO, is a stony asteroid and bright Mars-crosser from the innermost regions of the asteroid belt, approximately 7 kilometers in diameter. It was discovered on 26 September 1933, by Belgian astronomer Eugène Delporte at Uccle Observatory in Belgium.[3] Two nights later, Sonja was independently discovered by Soviet astronomer Grigory Neujmin at Simeiz on the Crimean peninsula. The origin of the asteroid's name is unknown.[2]

1293 Sonja
Discovery [1]
Discovered byE. Delporte
Discovery siteUccle Obs.
Discovery date26 September 1933
MPC designation(1293) Sonja
Named after
1933 SO
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc83.39 yr (30,458 days)
Aphelion2.8407 AU
Perihelion1.6138 AU
2.2272 AU
3.32 yr (1,214 days)
0° 17m 47.4s / day
Physical characteristics
Dimensions3.65±0.45 km[5]
7.23 km (derived)[4]
7.80±0.7 km (IRAS:3)[6]
2.876±0.001 h[a]
2.8768±0.0003 h[b][c]
2.87797±0.00002 h[d][e]
2.878±0.001 h[7]
2.8785±0.0001 h[8]
2.879±0.001 h[f][g]
2.879±0.002 h[9]
2.881±0.002 h[h]
0.1226 (derived)[4]
0.4598±0.095 (IRAS:3)[6]
SMASS = Sq [1] · S[4]
12.00[6] · 13.50[5] · 13.6[1][4] · 13.86±0.32[10]

Orbit and classificationEdit

In the SMASS taxonomy, Sonja is classified as a Sq-type, an intermediary between the abundant S and rather rare Q-type asteroids. It orbits the Sun in the inner main-belt at a distance of 1.6–2.8 AU once every 3 years and 4 months (1,214 days). Its orbit has an eccentricity of 0.28 and an inclination of 5° with respect to the ecliptic.[1] Sonja's observation arc begins with its official discovery observation at Uccle, as no precoveries were taken and no prior identifications were made.[3]

Physical characteristicsEdit

Rotation periodEdit

Several well-defined rotational lightcurves of Sonja were obtained from photometric observations during 2003–2016.[c][g] Light-curve analysis gave a concurring rotation period of 2.876–2.879 hours with a brightness variation between 0.14 and 0.21 magnitude.

In 2006, the first lightcurve was obtained by David Higgins (U=3),[7] followed by Federico Manzini and Vladimir Benishek (U=3/3-).[8][9] Photometric observations continued in August 2008, by Petr Pravec at Ondřejov Observatory (U=3),[d][e] and in 2016, four more lightcurves were obtained by Peter Kušnirák and Petr Pravec, as well as by Robert Stephens, Daniel Klinglesmith and Isaac Aznar (U=3/3/3/3).[a][b][f][h]

Diameter and albedoEdit

According to the surveys carried out by the Japanese Akari satellite and the Infrared Astronomical Satellite IRAS, Sonja measures 3.65 and 7.80 kilometers in diameter, and its surface has an exceptionally high albedo of 0.53 and 0.46, respectively.[5][6] This would make Sonja one of the brightest known Mars-crossing asteroids. However, the Collaborative Asteroid Lightcurve Link derives an albedo of 0.1226 and a diameter of 7.23 kilometers with an absolute magnitude of 13.6.[4]


It is unknown as to whether the name "Sonja" refers to any known place, person or occurrence. It was speculated that "Sonja" could have been chosen based on the two letter of its provisional designation, 1933 SO.[2] It is also speculated, that the name "Sonja" might have been on a list of generic German female names sent by the German ARI to several discoverers of minor planets in 1913, requesting the immediate naming of their discoveries in order to avoid confusion and possible errors (RI 1039; AN 196 and 137).[11]

Unknown meaningEdit

Among the many thousands of named minor planets, Sonja is one of 120 asteroids, for which no official naming citation has been published. All of these low-numbered asteroids have numbers between 164 Eva and 1514 Ricouxa and were discovered between 1876 and the 1930s, predominantly by astronomers Auguste Charlois, Johann Palisa, Max Wolf and Karl Reinmuth (also see category).[12]


  1. ^ a b Not yet available on SAO/NASA Astrophysics Data System (ADS): Klinglesmith 2017, see summary figures at LCDB entry for (1293) Sonja
  2. ^ a b Pravec (2016) web: light-curve taken on 2016-07-09. Rotation period 2.8768±0.0003 hours with a brightness amplitude of 0.18 mag and Quality Code of 3. Summary figures for (1293) Sonja at Collaborative Asteroid Lightcurve Link (CALL) and Pravec, P.; Wolf, M.; Sarounova, L. (2016)
  3. ^ a b Rotational light-curve plot of (1293) Sonja from 2016. Ondrejov Asteroid Photometry Project from unpublished data by Peter Kušnirák and Petr Pravec
  4. ^ a b Pravec (2008) web: rotation period 2.87797±0.00002 hours with a brightness amplitude of 0.16 mag. Summary figures for (1293) Sonja at Collaborative Asteroid Lightcurve Link (CALL) and Pravec, P.; Wolf, M.; Sarounova, L. (2008)
  5. ^ a b Rotational light-curve plot of (1293) Sonja from 2008. Ondrejov Asteroid Photometry Project from unpublished data by Petr Pravec
  6. ^ a b Not yet available on SAO/NASA Astrophysics Data System (ADS): Stephens 2017b, see summary figures at LCDB entry for (1293) Sonja
  7. ^ a b Rotational light-curve plot of (1293) Sonja from July 2016. Published at the Center for Solar System Studies (CS3) by Robert Stephens
  8. ^ a b Not yet available on SAO/NASA Astrophysics Data System (ADS): Aznar 2017b, see summary figures at LCDB entry for (1293) Sonja


  1. ^ a b c d e f "JPL Small-Body Database Browser: 1293 Sonja (1933 SO)" (2017-02-15 last obs.). Jet Propulsion Laboratory. Retrieved 26 July 2017.
  2. ^ a b c Schmadel, Lutz D. (2007). "(1293) Sonja". Dictionary of Minor Planet Names – (1293) Sonja. Springer Berlin Heidelberg. p. 106. doi:10.1007/978-3-540-29925-7_1294. ISBN 978-3-540-00238-3.
  3. ^ a b c "1293 Sonja (1933 SO)". Minor Planet Center. Retrieved 18 January 2017.
  4. ^ a b c d e f "LCDB Data for (1293) Sonja". Asteroid Lightcurve Database (LCDB). Retrieved 18 January 2017.
  5. ^ 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. Retrieved 18 January 2017.
  6. ^ 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. 12: IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 18 January 2017.
  7. ^ a b Higgins, David; Goncalves, Rui M. D. (March 2007). "Asteroid Lightcurve Analysis at Hunters Hill Observatory and Collaborating Stations - June-September 2006". The Minor Planet Bulletin. 34 (1): 16–18. Bibcode:2007MPBu...34...16H. ISSN 1052-8091. Retrieved 18 January 2017.
  8. ^ a b Behrend, Raoul. "Asteroids and comets rotation curves – (1293) Sonja". Geneva Observatory. Retrieved 18 January 2017.
  9. ^ a b Benishek, Vladimir (March 2008). "CCD Photometry of Seven Asteroids at the Belgrade Astronomical Observatory". The Minor Planet Bulletin. 35 (1): 28–30. Bibcode:2008MPBu...35...28B. ISSN 1052-8091. Retrieved 18 January 2017.
  10. ^ 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 18 January 2017.
  11. ^ Schmadel, Lutz D. (2007). "(579) Sidonia". Dictionary of Minor Planet Names – (579) Sidonia / ARI note from 1913. Springer Berlin Heidelberg. pp. 59–60. doi:10.1007/978-3-540-29925-7_580. ISBN 978-3-540-00238-3.
  12. ^ Schmadel, Lutz D. (2007). "Appendix 11 – Minor Planet Names with Unknown Meaning". Dictionary of Minor Planet Names – Fifth Revised and Enlarged revision. Springer Berlin Heidelberg. pp. 927–929. ISBN 978-3-540-00238-3.

External linksEdit