Astronomers estimate the mass of a galaxy by observing the motions of its stars and gas. By studying the dynamics of these components, such as their velocities and orbits, astronomers can infer the gravitational forces at work within the galaxy. Additionally, the presence of dark matter, which does not emit light but exerts gravitational influence, is also taken into account when estimating a galaxy’s total mass.
Come for the Scenery, Stay for the Stars