Galaxies

Definition

Galaxies are vast systems composed of stars, stellar remnants, interstellar gas, dust, and dark matter, bound together by gravity. They vary greatly in size and structure and are fundamental building blocks of the universe.

5 Must Know Facts For Your Next Test

1. There are three main types of galaxies: spiral, elliptical, and irregular.
2. Edwin Hubble's discovery in the 1920s confirmed that galaxies exist outside our Milky Way.
3. The Milky Way is a barred spiral galaxy containing over 100 billion stars.
4. Galaxy evolution is influenced by factors such as mergers and interactions with other galaxies.
5. Distant galaxies can be observed using telescopes like the Hubble Space Telescope to study their properties and evolution.

Review Questions

• What are the three main types of galaxies?
• Who confirmed the existence of galaxies beyond the Milky Way?
• How do mergers influence galaxy evolution?

Related terms

Spiral Galaxy: A type of galaxy characterized by a flat, rotating disk with spiral arms extending from a central bulge.

Elliptical Galaxy: A type of galaxy with an ellipsoidal shape that contains older stars and less interstellar material compared to spiral galaxies.

Dark Matter: A form of matter that does not emit light or energy but exerts gravitational effects on visible matter in the universe.