You look at a time exposure photograph of the night sky taken in the northern hemisphere and notice that each circumpolar star traces one-eighth of a complete circle around Polaris. What was the exposure time for the photograph?
A) 1 hour
B) 3 hours
C) 4 hours
D) 8 hours

Question

Quizplus · Accepted Answer

Since each circumpolar star traces one-eighth of a complete circle around Polaris, and it takes 24 hours for stars to complete a full circle (due to the Earth's rotation), the exposure time must be 24 hours / 8 = 3 hours.

You Look at a Time Exposure Photograph of the Night