Encyclopedia · Glossary
Galaxy
A gravitationally bound system of stars, gas, dust, and dark matter.
ScienceBeginner
Definition
A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas and dust, and dark matter. Galaxies range from dwarfs with a few million stars to giants containing hundreds of billions.
In context
Galaxies come in several broad shapes, including spirals, ellipticals, and irregulars. Our own galaxy, the Milky Way, is a barred spiral, and the Sun is just one of its many billions of stars.
Related ideas
Most large galaxies host a supermassive black hole at their center. Galaxies themselves cluster into larger groups and superclusters spread across the observable universe.