1. Hertzsprung-Russell Diagram

2. H-R Diagram
Compares the temperature, color and luminosity (brightness) of stars on a graph.
The temperature is the surface temperature of the star
The brightness of the star is its absolute magnitude

3. APPARENT MAGNITUDE VS. ABSOLUTE MAGNITUDE
Measure of the amount of a star’s light received on Earth
Apparent magnitude
Measure of the amount of light a star actually gives off
Absolute magnitude

4. Color indicates temperature
STAR PROPERTIES
Color indicates temperature
Hot stars are
Blue
Cool stars are
Red
Medium temperature stars are
Yellow

5. But not enough mass or heat to start fusion.
White dwarfs
small, hot stars
But not enough mass or heat to start fusion.
leftover centers of old stars

6. Red-Giants
Helium fuses into carbon.
When star runs out of energy, the center shrinks and the outer part expands outward. It will grow very large and cool.

7. Supergiants
Carbon fuses into iron
Very massive cool giant star

8. Main Sequence
Hydrogen fuses to Helium
Stretches diagonal from the top left to the right bottom
Our sun is an average main sequence star

9. Size and mass of stars increases as you go up and to the right on the HR diagram.

10. Temperature and brightness increases as you go up and to the left of HR Diagram.

11. Blue stars are on the left of the diagram, red stars on the right of the diagram.