Chapter 2 Lesson 2: Gravity and Structure in the Universe PDF

# UNIT: 1 ## Chapter: 2 - Stars and Light ### Lesson 2: Different Types of Galaxy ### VOCABULARY **Galaxy** - A collection of stars, interstellar gas, dust and remnants of stars that are all bound together by gravity. ### Types of Galaxies - **Spiral Galaxy** - **Elliptical Galaxy** - **Irregul...

# UNIT: 1 ## Chapter: 2 - Stars and Light ### Lesson 2: Different Types of Galaxy ### VOCABULARY **Galaxy** - A collection of stars, interstellar gas, dust and remnants of stars that are all bound together by gravity. ### Types of Galaxies - **Spiral Galaxy** - **Elliptical Galaxy** - **Irregular Galaxy** ### Three Types of Galaxy - **Spiral Galaxy** - It is a galaxy that contains a bulge, a disk and a halo. - **Elliptical Galaxy** - A galaxy shaped like an elongated sphere. - **Irregular Galaxy** - A galaxy that does not have the clearly defined shape and symmetry of a spiral galaxy or an elliptical galaxy. ### Spiral Galaxy - It is a bright mass of stars. - The stars are brightest near the center and less bright near the edges. ### Elliptical Galaxy - The stars in an elliptical galaxy tend to be older than those in a spiral galaxy. - Elliptical galaxy can vary greatly in size. ### Irregular Galaxy - They are usually much smaller than the other types of galaxy too. - Scientists classify them by how much structure they have. These galaxies have deformed. - This change in shape might be a result of even gravitational force or a collision with another galaxy. ### Formation of the Galaxy - Because of gravity, matter attracted other nearby matter. - The force of gravity became so great that stars formed within these clumps. - Small clusters of stars filled the universe. - These clusters of stars pulled on other clusters, and the clusters merged forming galaxies.