Why is rapid variability (over the course of weeks)a strong argument that quasars are powered by supermassive black holes?
A) Variability shows that black holes grow rapidly.
B) Variability shows that black holes are unstable.
C) Variability allows astronomers to estimate the size of the emitting region.
D) Variability rules out accretion disks as the source.

Question

Quizplus · Accepted Answer

Rapid variability over the course of weeks indicates that the emitting region must be very small, as changes in emission can occur very quickly. This implies that the emitting material must be very close to the black hole, as gravity weakens rapidly with distance. This is consistent with the idea that quasars are powered by accretion onto supermassive black holes, which can produce intense radiation from a small region. Therefore, variability can help astronomers estimate the size of the emitting region and provide evidence for the presence of supermassive black holes.

Why Is Rapid Variability (Over the Course of Weeks)a Strong