Early astronomers noticed that some stars in the sky appeared to move together across the sky as constellations. How do astronomers today explain this motion? The sun's gravity keeps the stars together because they orbit the sun at the same rate.
The sun's gravity keeps the stars together because they orbit the sun at the same rate.

The stars appear to move together along a path because of Earth's rotation on its axis.
The stars appear to move together along a path because of Earth's rotation on its axis.

Gravitational attraction between the stars keeps them fixed relative to each other as they move.
Gravitational attraction between the stars keeps them fixed relative to each other as they move.

The stars move around Earth in the same way, so their positions relative to each other stay the same.