What is a Galaxy? main content.

What is a Galaxy?

Part of Hall of the Universe.

Galaxies AMNH/D. Finnin

Galaxies are titanic swarms of tens of millions to trillions of stars, orbiting around their common center of gravity. They also contain interstellar gas and dust. Galaxies show a range of shapes that astronomers group into three basic classes: spiral, elliptical, and irregular.