They are proposed to be the primary cause of active galactic nuclei found at the core of some galaxies. (sciencedaily.com)
Originally, Shaya and colleagues were looking for active galactic nuclei in their Kepler data. (jpl.nasa.gov)
There have been a number of mechanisms proposed for quenching, for example «feedback» from supernovae or active galactic nuclei which breaks up the star forming clouds and reduces the star formation rate, but the measurement and verification of yet other possible processes is of great importance. (sciencedaily.com)