Quasars appear as unresolved points of light, as do stars, and hence quasars were thought to be a type of star until the 1960s. We now know that the brightest quasars lie far across the visible universe from us, and include the most distant objects known. Quasars may occupy the centers of galaxies and may even be much brighter than their host galaxies. In fact, the centers of many nearby galaxies have similarities to quasars - including the center of our own Milky Way Galaxy . The exact mechanism responsible for a quasar 's extreme brightness is unknown, but thought to involve supermassive black holes .
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