Quasars or quasi-stellar radio source are sources of electromagnetic energy which are characterized with high red shifts, thus leading scientists to conclude that not only they are moving away but are also at a great distance from us. Of the over 100,000 quasars identified to-date, the greatest proportion are over one billion light-years away (the closest quasar identified to-date is 780 million light-years away whereas the most distant quasar discovered so far is 13 billion light-years away). As a result, quasars represent entities from the universe's distant past.

Given their visibility (generally as point sources of light), it follows they must be associated with tremendous amounts of energy which is only exceeded in intensity by supernovae and gamma-ray bursts. Some examples of quasars also involve the centers of (active) galaxies and which has led to the suggestion that supermassive black holes at the galaxy center and the consequent accretion of material must fuel these quasars. The rapid change in luminosity observed for some quasars also suggests they must be relatively small entities.

A special group of quasars commonly referred to as blazars are characterized with very high luminosities and display variability in their magnitude which range from a few tenths to 3-4 units over the course of a few minutes to a few days. Blazars differ from regular quasars only because of perspective, for blazars have their relativistic jet pointing at earth, thus allowing the observer to peer directly into the jet itself and the ensuing emission activity that is present. The current belief is that blazars harbour a supermassive black hole with a blazer situated at each of the two opposing poles. To-date, 66 highly-probable blazars and another 27 suspected blazars have been discovered by the Compton Gamma-Ray Observatory and which are available in the Third EGRET catalog.

Note: Blazar 3C 454.3 in the constellation of Pegasus lies at a distance of approximately 7.7 billion light-years away and is one of the most distant blazars from earth. With a visual magnitude of 16.10 (v), it is slightly out of reach of most amateur equipment. With a sizeable redshift of 0.859001, this faint but highly red-shifted quasar is receeding away from us at 165,232 km/sec or about 55% the speed of light!

Blazar 3C 454.3 has a history of previous flares and including the 2005 event when it was closely monitored by both the Spitzer Space Telescope and the Chandra X-ray Observatory when its brightness reached the equivalent of 550 billion suns. The blazar would flare once again in 2007 whereas the image below represents the most recent such event where an outburst leading to an increase in brightness by about five magnitudes was first noted in May/2014. Blazar 3C 454.3 is considered one of the brightest and most persistent gamma-ray sources in the sky and can be found in the immediate vicinity of Markab (α-Peg, mag 2.45) where it forms a tight visual double with GSC 1698-0718 (mag 13.1). Further details in relation to blazar 3C 454.3 are available on Simbad and NASA's NED database.