Asteroids

After discussing the mass, diameter, and density of asteroids, a description is given of the taxonomic system. It is noted that the classification scheme is based on the following parameters: geometric albedo, minimum of the polarization curve, color index in the UBV system, and characteristics in the reflectance spectra. Asteroids exhibit fluctuations in brightness with periods of several hours; these are due mainly to their rotation around a spin axis. Attention is also given to Hirayama families and groups, to resonances, and to the relationship with meteorites and comets.