Why Do Astronomers Think That There Are Fewer Quasars Today

question 7

Multiple Choice

Why do astronomers think that there are fewer quasars today than there were billions of years ago?

• A) quasars are seen when the supermassive black hole at the center of a galaxy has a lot of "food to eat" (stars and gas) and the amount of available food tends to decrease with time
• B) quasars are supermassive black holes at the centers of galaxies, and such black holes are constantly losing mass and thus getting less and less able to pull on anything
• C) quasars tend to merge all the time, and so there are fewer and fewer of them as time goes on
• D) quasars are caused by many supernovae going off at the same time, and massive stars only exploded in the early history of the universe; they don't explode today
• E) no one has the slightest idea on how to answer this question; it is completely unsolved

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