They are compact intense sources of x-rays as wells as visible light, and can be brighter than hundreds of galaxies put together.
Quasars look starlike when viewed through an optical telescope.
It wasn't until the 1950's when radio astronomy was first developed, that astronomers realized that they were emitting enormous amounts of radio energy. These objects were named quasars, short for quasi-stellar radio sources. The source of the prodigious energy output of quasars is believed to be a supermassive black hole in the center of a galaxy. Cosmic jets are a common feature of quasars and active galaxies. They are believed to be produced by enormous electromagnetic forces near the central black hole.