Download Unit D, Chapter 2, Lesson 3

Chapter Outline
Unit D, “The Solar System and Beyond”
Chapter 2, “The Sun and Other Stars”
Lesson 3, “What Are Galaxies?”, pgs. D46 – D49
The Milky Way Galaxy
Define Universe – everything that exists
Although it seems crowded, most of the universe is ___empty_______.
Define Galaxy – a group of stars, gas, and dust
What is the name of Earth’s galaxy?
Milky Way Galaxy
Our galaxy is one of the largest in the universe; it would take the light from a star on one
side of the galaxy how long to reach the other side?
100,000 light-years
Types of Galaxies
Galaxies are classified by ____shape______. Name the four basic types.
1. spiral galaxy
2. elliptical galaxy
3. irregular galaxy
4. barred spiral galaxy
What shape is our galaxy?
Spiral galaxy
Define Light-Year – the distance light travels in one Earth year, about 9.5 trillion km
About half of all galaxies are __________Elliptical__________.
Galactic Clusters and Nebulae
What is a galactic cluster?
A group of galaxies
The Milky Way Galaxy is one of about 30 galaxies in a cluster called …
Local Group
What are nebulae?
Where stars form, the first stage of a star
A nebula has no __light________ of its own.