How are astronomers able to determine that quasars are so small
A)They are variable over a short period of time.
B)They emit mainly X-rays.
C)They are only found at very large distance.
D)The structure of a quasar is completely resolved in images.

Question

Quizplus · Accepted Answer

Astronomers are able to determine that quasars are small because they show variability over a short period of time, sometimes as short as hours or days. This indicates that the source of the radiation is very small, possibly the size of a solar system or even smaller.

How Are Astronomers Able to Determine That Quasars Are So