1180 Rita, provisional designation 1931 GE, is a dark and spheroidal Hildian asteroid from the outermost regions of the asteroid belt, approximately 97 kilometers in diameter. It was discovered on 9 April 1931, by German astronomer Karl Reinmuth at the Heidelberg Observatory in southwest Germany. Any reference of its later name, "Rita", is unknown.
Orbit and classification.
"Rita" belongs to the orbital Hilda group which is located in the outermost part of the main-belt. Asteroids in this dynamical group have semi-major axis between 3.7 and 4.2 AU and stay in a 3:2 resonance with the gas giant Jupiter. "Rita", however, is a background asteroid and not a member of the (collisional) Hilda family (101). Hildian asteroids are thought to have originated from the Kuiper belt.
The asteroid orbits the Sun at a distance of 3.4–4.6 AU once every 7 years and 12 months (2,906 days). Its orbit has an eccentricity of 0.16 and an inclination of 7° with respect to the ecliptic.
It was first observed as A907 GG at Heidelberg in 1907. The body's observation arc begins at Heidelberg in 1908, when it was identified as A908 KA, approximately 23 years prior to its official discovery observation.
Physical characteristics.
In the Tholen taxonomy, "Rita" is a dark and reddish P-type asteroid. The P-type asteroids are some of the darkest objects in the Solar System.
Rotation period.
Since 1983, several rotational lightcurves of "Rita" have been obtained from photometric observations. Lightcurve analysis gave a wide range of divergent rotation periods between 9 and 20.5 hours. The "Light Curve Data Base" adopts a period of 13.090 hours with a brightness amplitude of 0.06 magnitude. Bodies with such a low brightness variation are typically of a spherical rather than elongated shape. The lightcurve was obtained in January 2017, by American astronomer Brian Warner at the Center for Solar System Studies in California ().
Diameter and albedo.
According to the surveys carried out by the Japanese Akari satellite, and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, "Rita" measures 97 kilometers in diameter and its surface has an albedo between 0.041 and 0.058. The "Collaborative Asteroid Lightcurve Link" assumes a standard albedo for carbonaceous, outer main-belt asteroids of 0.057, and calculates a diameter of 82.72 kilometers with on an absolute magnitude of 9.14.
Naming.
Any reference of this minor planet's name to a person or occurrence is unknown.
Unknown meaning.
Among the many thousands of named minor planets, "Rita" is one of 120 asteroids, for which no official naming citation has been published. All of these low-numbered asteroids have numbers between and and were discovered between 1876 and the 1930s, predominantly by astronomers Auguste Charlois, Johann Palisa, Max Wolf and Karl Reinmuth.
References.
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