Galaxy - Outside Of The Galaxy, Classification Of Galaxies, Elliptical Galaxies, Spiral Galaxies, Irregular Galaxies

A galaxy is a large collection of stars similar to the Milky Way galaxy in which our solar system is located. Astronomers classify galaxies according to their shape as either spiral, elliptical, or irregular. Spiral galaxies are further subdivided into normal and barred spirals. Elliptical galaxies can be either giant or dwarf ellipticals, depending on their size.

Galaxies can contain anywhere from a few million stars, for dwarf ellipticals, to a few trillion stars, for giant ellipticals or spirals. Galaxies emitting far more energy than can easily be explained by a collection of stars are classified as active galaxies. The study of other galaxies in addition to being intrinsically interesting both helps us understand our own Milky Way galaxy and gives us clues to understanding the universe as a whole.