Astronomers study stars by looking through telescopes. Telescopes make stars and planets look bigger. Telescopes let us see two stars that are close together like Mizar A and Mizar B. Telescopes also let us see stars that are too faint to be seen with the eye. Astronomers also study stars by passing their light through a glass prism or a diffraction grating. Planets shine with reflected light.
Planets move around stars.
The time from one new Moon to the next is the Moon's synodic period . This is where our month comes from. As the Moon travels around the Earth it always keeps the same face toward the Earth. This is called synchronous rotation . This occurs because the Moon is tidally locked to the Earth.