1. Star Classification

2. Stars can be classified in three ways:
Size
Temperature
Brightness/Magnitude

3. Size
How massive the star is

4. Temperature
Color = temperature – a star’s color indicates the temperature of its surface
The hottest stars appear blue.
The coolest stars appear red.

5. Brightness or Magnitude
Magnitude: The amount of light a star gives off depends on its size and temperature.
How bright a star looks from Earth depends upon both how far the star is from Earth and how bright the star actually is.
A stars brightness can be can be described in two ways: apparent magnitude and absolute magnitude.

6. Apparent vs. Absolute Magnitude
Apparent magnitude is the brightness of a star as seen from Earth.
Absolute magnitude is brightness of a star as if it were 32.6 light years from Earth or the actual brightness of the star.
The brightness of the stars is compared to the brightness of our Sun. We call this luminosity.