Why are quasars rare today?
A) The Universe's expansion has spread out the quasars.
B) The black holes are too massive to be classified as quasars.
C) There is so much dust today that it obscures quasar emission.
D) Little gas is left to accrete onto supermassive black holes.

Question

Quizplus · Accepted Answer

Quasars are powered by the accretion of gas onto supermassive black holes. As the Universe continues to age, less gas is available to be accreted onto these black holes, leading to a decrease in the number of actively shining quasars.

Why Are Quasars Rare Today