How can we tell that some stars are relatively close to us in the sky
A)Some stars are occasionally eclipsed by the Moon, so they must be nearby.
B)Some stars vary in brightness caused by sunspots we can see because they are so close.
C)Some stars appear to be extremely bright and must therefore be very close to us.
D)Some stars appear to move periodically back and forth against the background stars because of Earth's movement around the Sun.

Question

Quizplus · Accepted Answer

Stars that appear to move periodically back and forth against the background stars because of Earth's movement around the Sun are relatively close to us in the sky. This apparent movement is called parallax, and astronomers use it to determine the distance to nearby stars. The larger the parallax angle, the closer the star is to us.

How Can We Tell That Some Stars Are Relatively Close