A galaxy is a huge collection of stars, planets, gas, and dust held together by gravity. It is like a big family of stars living in space. Full definition
Another measure comes from counting the number of clusters of galaxies in the universe to measure the volume of space and the rate at which that volume is increasing. (britannica.com)
The researchers measured the star formation activity in galaxies located in different environments. (sciencedaily.com)
The dwarf galaxies far away are too faint to be seen and are, therefore, overlooked in surveys of the sky. (astronomynotes.com)