Discovered by E. Delporte MPC designation 1293 Sonja Alternative names 1933 SO Discovered 26 September 1933 Orbits Sun Asteroid group Mars-crosser asteroid | Discovery date 26 September 1933 Named after unknown Minor planet category Mars-crosser Absolute magnitude 12 Discoverer Eugène Joseph Delporte | |
Discovery site Royal Observatory of Belgium Similar 132 Aethra, 2101 Adonis, 512 Taurinensis, 1221 Amor, Sun | ||
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. 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.
Description
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 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. Sonja's observation arc begins with its official discovery observation at Uccle, as no precoveries were taken and no prior identifications were made.
Several well-defined rotational light-curves of Sonja were obtained from photometric observations during 2003–2016. 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 light-curve was obtained by David Higgins (U=3), followed by Federico Manzini and Vladimir Benishek (U=3/3-). Photometric observations continued in August 2008, by Petr Pravec at Ondřejov Observatory (U=3), and in 2016, four more light-curves were obtained by Peter Kušnirák and Petr Pravec, as well as by Robert Stephens, Daniel Klinglesmith and Isaac Aznar (U=3/3/3/3).
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. 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 using an absolute magnitude of 13.6.
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. 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). There are about 120 minor planets with no published naming citation (also see Category:Minor planets with names of unknown origin).