Galaxies

A galaxy is a massive, gravitationally bound system that consists of stars, stellar remnants, an interstellar medium of gas and dust, and dark matter. Galaxies are the building blocks of the universe, and they come in various shapes and sizes.

Types of Galaxies

There are three main types of galaxies:

1. Spiral Galaxies: These galaxies have a central bulge with spiral arms extending outward. The Milky Way is an example of a spiral galaxy.
2. Elliptical Galaxies: These galaxies are shaped like ellipsoids and are generally older and contain mostly older stars. They have little interstellar matter.
3. Irregular Galaxies: These galaxies do not have a distinct regular shape and often contain large amounts of gas and dust, which leads to ongoing star formation.

Galaxy Formation

Galaxies are thought to have formed from the gravitational collapse of clouds of gas, and they continue to evolve through interactions with other galaxies. The study of galaxies and their formation is an important area of research in astronomy.

Study Guide

1. What is a galaxy and what does it consist of?
2. List and describe the three main types of galaxies.
3. How are galaxies thought to have formed?
4. Why is the study of galaxies important in astronomy?

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