Satellites have been discovered around asteroids belonging to all major dynamical and taxonomic classes. The discoveries have been made with space missions, radar observations, photometric lightcurves, and high resolution imaging from the ground and space. The properties of each major population are widely different, and different formation mechanisms dominate in each population: dynamical capture mechanisms in the Kuiper Belt, collisions in the Main Belt, and the thermal YORP-effect among near-Earth Asteroids (NEAs). We will focus on the YORP (Yarkovsky-Keefe-Radzievskii-Paddack) effect, and show how the torques created by anisotropic reflection and thermal re-emmision of sunlight lead to spin-up, disruption and satellite formation among NEAs.
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