1233 Kobresia

1233 Kobresia, provisional designation, is a carbonaceous background asteroid from the central regions of the asteroid belt, approximately 33 kilometers in diameter. It was discovered on 10 October 1931, by German astronomer Karl Reinmuth at the Heidelberg Observatory in southwest Germany. The asteroid was named for the grass-like flowering plant Kobresia, a genus in the sedge family.

Orbit and classification
Kobresia is a non-family asteroid from the main belt's background population. It orbits the Sun in the central main-belt at a distance of 2.4–2.7 AU once every 4 years and 1 month (1,493 days; semi-major axis of 2.56 AU). Its orbit has an eccentricity of 0.06 and an inclination of 6° with respect to the ecliptic.

The body's observation arc begins with its first observation as at Heidelberg in October 1927, or four years prior to its official discovery observation.

Physical characteristics
Kobresia has been characterized as a carbonaceous C-type asteroid by Pan-STARRS photometric survey.

Rotation period
Two rotational lightcurves of Kobresia were obtained by French amateur astronomer Pierre Antonini. Lightcurve analysis of his photometric observations made in 2004 and 2006, gave a rotation period of 27.76 and 27.83 hours with a brightness amplitude of 0.32 and 0.34 magnitude, respectively (U=2/2). While not being a slow rotator, Kobresia's period is longer than that of the average asteroid.

Diameter and albedo
According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Kobresia measures between 29.73 and 36.167 kilometers in diameter and its surface has an albedo between 0.0305 and 0.0475.

The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0396 and a diameter of 33.45 kilometers based on an absolute magnitude of 11.5.

Naming
This minor planet was named after a genus in the family Cyperaceae, Kobresia, a grass-like flowering plant, commonly known as "bog sedges". The author of the Dictionary of Minor Planet Names contacted Dutch astronomer Ingrid van Houten-Groeneveld in order to confirm the meaning of this asteroid's name.

Meta-naming
The initials of the minor planets through, all discovered by Reinmuth, spell out "G. Stracke". Gustav Stracke was a German astronomer and orbit computer, who had asked that no planet be named after him. In this manner Reinmuth was able to honour the man whilst honoring his wish. Nevertheless, Reinmuth directly honored Stracke by naming planet later on. The astronomer Brian Marsden was honored by the same type of meta-naming using consecutive initial letters in 1995, spelling out "Brian M." in the sequence of minor planets through.

Reinmuth's flowers
Due to his many discoveries, Karl Reinmuth submitted a large list of 66 newly named asteroids in the early 1930s. The list covered his discoveries with numbers between and. This list also contained a sequence of 28 asteroids, starting with 1054 Forsytia, that were all named after plants, in particular flowering plants (also see list of minor planets named after animals and plants).