3184 Raab

3184 Raab, provisional designation, is a dark background asteroid and a potentially slow rotator from the central regions of the asteroid belt, approximately 17 km in diameter. It was discovered on 22 August 1949, by South African astronomer Ernest Leonard Johnson at the Union Observatory in Johannesburg. The likely C-type asteroid could have a long rotation period of 275 hours. It was named after Austrian amateur astronomer and software engineer Herbert Raab.

Orbit and classification
Raab 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 2.0–3.4 AU once every 4 years and 4 months (1,593 days; semi-major axis of 2.67 AU). Its orbit has an eccentricity of 0.26 and an inclination of 8° with respect to the ecliptic. The body's observation arc begins with its official discovery observation at Johannesburg in August 1949.

Physical characteristics
This asteroid's spectral type is unknown. Based on its low albedo, measured by the Wide-field Infrared Survey Explorer (WISE), Raab is possibly C-type asteroid.

Rotation period
In December 2011, a rotational lightcurve of Raab was obtained from photometric observations in the R-band by astronomers at the Palomar Transient Factory in California. Lightcurve analysis gave a rotation period of 274.944 hours with a brightness amplitude of 0.09 magnitude. However, the lightcurve is only fragmentary and could be completely wrong (U=1). This makes Raab only a potentially slow rotator rather than a confirmed one. As of 2018, no follow up observations have been published.

Diameter and albedo
According to the surveys carried out by the Japanese Akari satellite and the NEOWISE mission of NASA's WISE telesecope, Raab measures between 15.28 and 19.280 kilometers in diameter and its surface has an albedo between 0.036 and 0.086.

The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.10 – used as a generic compromise between the stony (0.20) and carbonaceous (0.057) asteroids with semi-major axis between 2.6 and 2.7 AU – and consequently calculates a shorter diameter of 13.25 kilometers using on an absolute magnitude of 12.51.

Naming
This minor planet was named after Austrian amateur astronomer and software engineer Herbert Raab (born 1969), who developed the astrometric software "Astrometrica". The official naming citation was published by the Minor Planet Center on 3 May 1996 (M.P.C. 27124), following a proposal by Brian Marsden and Gareth Williams.