Andromeda galaxy

Definition

The Andromeda Galaxy, also known as M31, is the closest spiral galaxy to the Milky Way and is on a collision course with it. It is approximately 2.537 million light-years from Earth and is the largest galaxy in the Local Group.

5 Must Know Facts For Your Next Test

1. Andromeda Galaxy contains roughly one trillion stars, more than twice the number of stars in the Milky Way.
2. It has a diameter of about 220,000 light-years, making it significantly larger than the Milky Way.
3. Andromeda and the Milky Way are expected to collide in about 4.5 billion years, forming a new galaxy.
4. It's visible to the naked eye from Earth under dark sky conditions.
5. Andromeda has a supermassive black hole at its center, similar to many other large galaxies including our own.

Review Questions

• How far is the Andromeda Galaxy from Earth?
• What significant event involving Andromeda and the Milky Way is predicted to occur in about 4.5 billion years?
• Approximately how many stars does Andromeda contain compared to the Milky Way?

Related terms

Local Group:

A galaxy group that includes the Milky Way, Andromeda, and about 54 other smaller galaxies.

Spiral Galaxy: A type of galaxy characterized by its flat, rotating disk containing stars, gas, dust, and often a central bulge with spiral arms.

Supermassive Black Hole:

An extremely large black hole found at the center of many galaxies including both Andromeda and the Milky Way.