Hertzsprung-Russell Diagram

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

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

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

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

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.

Supergiants Carbon fuses into iron Very massive cool giant star

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

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

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

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