What Is a Galaxy?
Are you looking for an easy way to teach your child about space? We’ve put together a set of free materials that parents and teachers can use right away. In this lesson, your child will dive into the fascinating world of galaxies.
We’ll explore the types and organization of galaxies in the vast universe. Explore science in a more engaging way with captivating 3D videos and interactive quizzes. Download our app to get started!
Table of Contents
What You Will Learn from This Lesson
- A galaxy is made of stars, interstellar gas, and dark matter.
- Galaxies are spiral, elliptical, or irregular types.
- Galaxies group into galaxy groups, clusters, and superclusters.
Galaxies are systems composed of stars and interstellar matter. A typical galaxy can contain anywhere between ten million and trillions of stars. Astronomers estimate there could be trillions of galaxies in the universe.
What Are Galaxies Made Of?
A galaxy is composed of stars, interstellar gas, and dark matter. The diameter of a galaxy can range from hundreds to thousands of light-years across. The universe is enormous, and there are more galaxies than there are grains of sand on Earth.
How Many Types of Galaxies Exist?
Galaxies are classified into three main types: spiral galaxies, elliptical galaxies, and irregular galaxies. Two-thirds of all galaxies are spiral galaxies.
- Spiral Galaxies: These have a central glowing galactic bulge. A galactic disk with bright spiral arms surrounds the bulge. Our Milky Way is a spiral galaxy and is also a barred spiral galaxy because of a central bar-shaped structure.
- Elliptical Galaxies: These galaxies are smooth, oval-shaped, and lack obvious spiral arms or dust lanes.
- Irregular Galaxies: These galaxies do not have a particular shape or a bulge. About one-fourth of all galaxies are irregular galaxies. Their irregular shapes can be caused by strong gravitational forces pulling on other galaxies.
How Do Galaxies Group?
Galaxies tend to group to form larger structures.
- Galaxy Group: A Galaxy Group is a small family of galaxies comprising about 50 or fewer members.
- Galaxy Cluster: A larger structure formed when many galaxy groups combine.
- Supercluster: Different galaxy clusters can form a supercluster.
Fun Fact
- There are likely more galaxies in the universe than there are grains of sand on Earth.
- The Andromeda Galaxy is the closest galaxy to us.
- The diameter of some galaxies can be thousands of light-years across.
Vocabulary
- Galaxies: Systems of stars and interstellar matter.
- Spiral Galaxies: Galaxies with a central bulge, a disk, and bright spiral arms.
- Elliptical Galaxies: Galaxies that are smooth and oval-shaped, lacking obvious spiral arms or dust lanes.
- Irregular Galaxies: Galaxies that do not have a defined regular shape.
- Galaxy Group: A structure in the universe formed by fewer than 50 galaxies.
- Galaxy Cluster: A larger structure formed when many galaxy groups come together.
- Supercluster: A massive structure in the universe formed by different galaxy clusters.