Galaxies are typically classified into three main types based on their shape and structure:
-
Spiral Galaxies: These galaxies have a flat, rotating disk containing stars, gas, and dust, as well as a central concentration of stars known as the bulge. They are characterized by their spiral arms that extend outward from the center. The Milky Way, the galaxy that Earth is part of, is a classic example of a spiral galaxy.
-
Elliptical Galaxies: These galaxies range from nearly spherical to elongated shapes and lack the distinct features of spiral galaxies. They contain older stars and exhibit less gas and dust, resulting in less star formation compared to spiral galaxies. They can be further classified based on their eccentricity, from more spherical to more elongated forms.
-
Irregular Galaxies: As the name suggests, irregular galaxies do not have a defined shape or structure like spiral or elliptical galaxies. They often have chaotic appearances, lacking a central bulge and spiral arms. Irregular galaxies typically contain young stars and regions of active star formation.
Earth is part of the Milky Way Galaxy, which is classified as a spiral galaxy.