What is a quasi-stellar object, or QSO?
Black Holes in Galaxies
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A quasi-stellar object (QSO) is the general term given to an AGN that has very high luminosity. QSOs are so named because in typical astronomical images taken in visible light they usually look like stars, or stars with a little bit of fuzz or structure surrounding them. In fact, they are not stars at all, but they are so luminous compared to their host galaxy that they drown out the light from it.