Although quasars appear faint when viewed from Earth, they are visible from extreme distances, being the most luminous objects in the known universe. The brightest quasar in the sky is 3C 273 in the constellation of Virgo. It has an average apparent magnitude of 12.8 (bright enough to be seen through a medium-size amateur telescope), but it has an absolute magnitude of −26.7. From a distance of about 33 light-years, this object would shine in the sky about as brightly as the Sun. This quasar's luminosity is, therefore, about 4 trillion (4) times that of the Sun, or about 100 times that of the total light of giant galaxies like the Milky Way. This assumes that the quasar is radiating energy in all directions, but the active galactic nucleus is believed to be radiating preferentially in the direction of its jet. In a universe containing hundreds of billions of galaxies, most of which had active nuclei billions of years ago but only seen today, it is statistically certain that thousands of energy jets should be pointed toward the Earth, some more directly than others. In many cases it is likely that the brighter the quasar, the more directly its jet is aimed at the Earth. Such quasars are called blazars.
aLthougH quasArS appear faInt WhEn viewed froM earth tHey ARe visible FrOm eXTREmE diSTAnCeS, BeINg thE moST lumiNouS ObjeCts in the knoWN uNivErSe the BrighteSt quASar iN the sKY IS 3C 273 iN the ConSteLlation of ViRgo. it HaS .an aveRage apPAREnT magniTUde of 12.8 (BriGht enOUgh To be seen thRoUgh a medIUm-sIze amateuR telEScOpe), but it has an aBsOLUTe magNitude oF −26.7. From A distaNce of abouT 33 LIgHT-yeARs, This ObjEct would sHine IN ThE SkY aBOut aS BriGHtlY AS tHe sUn. this qUasar's luminosiTy iS, thErefore, aBout 4 trilLion (4) tiMes that oF ThE sun, OR abOuT 100 TiMes THAt of the tOtAL lighT OF GIant galaxieS likE the milky way this asSUmeS that the QUAsAR is radiatinG ENergY iN All dirECtions, But thE ActiVe galacTic nucle.us is belIeveD to bE RaDIaTING prEFErentialLy IN tHe dIReCtIon of itS JEt. IN A univerSe conTaining hundrEds of bilLiONS of galAxIes, moSt of whiCH HaD ACtIvE nUclEi bIlliONs Of yeArs Ago But oNlY seen ToDAY, it is STa,tistIcaLLy CertAIn ThAt thOuSanDs of energY jetS SHOulD be pOInTed toWard tHE earTh, somE more direcTly Than oTheRs. iN manY caseS It Is liKEly ThAt The brigHter the quAsAR, tHe mORe dirEcTly Its jEt Is Aimed at THe earth. suCh quASars are Called blazars.