1 A compact, highly luminous region (often called a bright spot) in a cataclysmic binary, located either where the stream of material hits the edge of the accretion disk, or at the inner edge of the disk. There may be small-scale flickering or larger variations in luminosity depending on fluctuations in the rate of mass transfer. The presence of a hot spot is often indicated by a hump in the orbital light-curve.
2 A small, bright region in a lobe of a radio galaxy. It is believed to be the site where high-velocity material in a jet collides with the leading boundary between the lobe and the surrounding intergalactic medium.