This category of objects includes LINERs and "BL Lac's, Type I  and II Seyferts, blazars, and even quasars. They are regions at  the centers of galaxies * which emit tremendous amounts of  radiation; 
This category of objects includes LINERs and "BL Lac's, Type I  and II Seyferts, blazars, and even quasars. They are regions at  the centers of galaxies * which emit tremendous amounts of  radiation; the only known mechanism which can produce so much  energy is matter spiralling into a black hole as massive as a  million stars. FTP, what is this class of objects, an example of  which may be harbored in the center of our own Milky Way?
This category of objects includes LINERs and "BL Lac's, Type
{A}ctive {G}alactic {N}uclei (accept "active  galaxies" before the asterisk)