These small, faint systems made up of millions or billions of stars, dust, and gas constitute the most common type of galaxy observed in the universe. (sciencedaily.com)
There are two main types of galaxies: «blue», star - forming galaxies and «red and dead» galaxies that no longer form new stars. (newscientist.com)
The rate of star formation may be the determining factor in what type of galaxy will form. (astronomynotes.com)