What observational evidence suggests that the centers of quasars are small, about a fraction of a light-year?
A) the fact that quasars are so distant, and therefore are very young
B) photographs of quasars
C) They emit radiation over a very wide range of wavelengths
D) The intensity of their radiation fluctuates over periods of months
E) All of these choices are correct.

Question

Quizplus · Accepted Answer

The intensity of their radiation fluctuates over periods of months, indicating that the emitting region is small, as changes in brightness occur over timescales that correspond to the size of the region.

What Observational Evidence Suggests That the Centers of Quasars Are