Elliptical Galaxies

Elliptical galaxies are one of the three main types of galaxies, along with spiral and irregular galaxies. They are characterized by their smooth, oval or elliptical shape and lack of significant structure such as spiral arms. Elliptical galaxies are composed mainly of older stars, and they have very little interstellar gas and dust compared to spiral galaxies.

Formation

Elliptical galaxies are thought to form through the merging of smaller galaxies. When two or more galaxies collide, their stars and gas clouds mix together and eventually settle into a new, larger elliptical galaxy. This process can result in the formation of giant elliptical galaxies, some of which can contain trillions of stars.

Classification

Elliptical galaxies are classified according to their shape, ranging from nearly spherical (E0) to highly elongated (E7). The classification is based on the ratio of the major and minor axes of the galaxy's apparent elliptical shape as seen from Earth.

Study Guide

1. What are the main characteristics of elliptical galaxies?
2. How are elliptical galaxies thought to form?
3. What is the classification system for elliptical galaxies based on?
4. Compare and contrast elliptical galaxies with spiral galaxies.
5. Research and describe a specific example of a well-known elliptical galaxy.

By studying and understanding elliptical galaxies, we can gain insights into the evolution of galaxies in the universe and the processes that shape their structures.