This illustration shows a possible view of a binary system between a black hole and a massive star. The star ejects gas in the form of a stellar wind. Much of this gas is collected in a disk around the black hole. When it is funnelled and accelerated into the disk, the gas releases a large amount of energy from gamma rays to visible and infrared light. However, the remaining gas surrounding the black hole forms a thick cloud which blocks most of the radiation. Only the very energetic gamma rays can escape and be detected.