What is a Galaxy?
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.
Keywords: Astrophysics, Cosmic dust, Galaxies, Gases
The Local Group of galaxies contains a few dozen members, bound together by gravity. Of these, our Milky Way and the Andromeda Galaxy are the largest.