Active Galactic Nuclei (AGNs) consists of galaxies with extremely bright nucleus, so much so, that they usually outshine the light from other galaxy parts such as arms or bulges. The reason behind intense power of AGN is believed to be the super massive black hole accreting matter from its vicinity at the center of galaxy. Sometimes, such systems are known to erupt powerful, narrow beam of high velocity charged particles. If one happens to view such a systems along the line of sight of these eruptions (jets) are called blazars. The emission from blazar jets is Doppler boosted, leading to extreme luminosities and flux variability and apparent superluminal motion shown by the ejecta. Not only such systems show extreme luminosities, it also varies on all observable timescales ranging from years to minutes with amount of energy dissipated equal to a million Suns in few hours timescale.
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