Question

when does the quasar stage of a galaxys life end? the quasar will eventually collapse into a supermassive black hole and disappear from view. as the universe expands, the galaxy cools too much to emit large amounts of radiation, and ceases to be a quasar. it ends when there is no longer enough gas to sustain a high level of accretion onto the hole. actually, a galaxy with quasar activity will always be a quasar.

Explanation:

Quasars are powered by the accretion of material onto supermassive black - holes. When there is insufficient gas to sustain a high - level of accretion onto the black hole, the energy production that characterizes the quasar phase stops, and the quasar stage ends. A quasar doesn't collapse into a supermassive black hole as it already has one at its core. The cooling due to the Universe's expansion is not the main factor for the end of the quasar stage. And a galaxy doesn't always remain a quasar.

Answer:

It ends when there is no longer enough gas to sustain a high level of accretion onto the hole.