For years controversy simmered as to whether quasars were isolated objects not associated with clusters of galaxies, or whether they were the cores of otherwise "normal" galaxies undergoing violent explosions. In the latter case surrounding galaxies may have been missed because the quasar so dramatically outshines it. A quasar may shine 100 times more brightly than a galaxy containing a hundred billion stars. (If a quasar phenomenon occurred at the center of our Milky Way, located 25,000 light-years away, the quasar would appear as bright as the moon.)
Painstaking research by many astronomers revealed that some quasars are indeed enormously luminous explosive nuclei of elliptical galaxies. These explosions are so bright that, because of the glare, we can barely see the surrounding galaxy. Only through use of very sophisticated photographic techniques and the largest optical telescopes have the parent galaxies been revealed in some of the closer quasars. Furthermore, because of the enormous distance to such objects, the surrounding clusters of galaxies are often invisible.
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