We can tell that some stars are relatively close to us in the sky because
A) they appear to move periodically back and forth against the background stars because of Earth's movement around the Sun.
B) they appear to be extremely bright.
C) they are occasionally occulted or eclipsed by our Moon.
D) the light from these stars shows only a very small redshift caused by the universal expansion of the universe.

Question

Quizplus · Accepted Answer

The periodic back and forth movement of stars against the background stars is called parallax, and it is caused by Earth's movement around the Sun. This allows us to calculate the distance to these stars.

We Can Tell That Some Stars Are Relatively Close to Us