1. The Hertzsprung – Russell Diagram
Astronomers use the H-R diagram to…
* Show what stars are made of by looking at their color.
*Compare the colors, brightness, temperature, and mass of stars.

2. The Hertzsprung – Russell Diagram
*Look at the two stars, Sun and Zeta Eridani.
Compare the two stars based on color, surface temp., and magnitude (brightness).
Sun is yellow– Zeta Eridani is Blue. Color is due to a stars temperature.
Sun temp. is much lower(6,000 K) – Zeta Eridani temp. is much higher(40,000 K)
Sun is average magnitude – Zeta Eridani is very high magnitude.
Sun and Zeta Eridani are Main Sequence stars. Incresed temp. = Increased Magnitude

3. Characteristics of a Galaxy
A Galaxy is a large group of stars, gas, and dust
held tighter by gravity.

4. Types of Galaxies Spiral Galaxy
*Have spiral areas that wind outward from inner regions.
*The arms are made up of stars and dust.
*Milky Way (our universe is a spiral).
*Brightest stars.
*Most common galaxy.

5. *Shaped like large three –dimensional ellipses.
Types of Galaxies
Elliptical Galaxy
*Shaped like large three –dimensional ellipses.
*Oldest stars.

6. *Smaller than other types of galaxies.
Irregular Galaxy
*Have many shapes
*Smaller than other types of galaxies.
*Newest stars.

7. Universe from Largest to Smallest
Galaxy
Solar System
Planet