THE LIFE CYCLE OF STARS Chapter 15 – 2 Part 2

A Tool for Studying Stars A Danish astronomer, Ejnar Hertzsprung, and American astronomer, Henry Russel, compared the brightness and temperature of stars on a graph. This became know as the HR diagram. It shows how stars are classified and how they change over time.

The HR Diagram The H-R diagram shows the relationship between the star’s surface temperature and its absolute magnitude.

Absolute magnitude (brightness) is on the y-axis. Bright stars are at the top and dim stars are at the bottom. Temperature is usually on the x-axis, along with the spectral type. Hot stars are on the left, cool stars on the right

Red Giants and supergiants are very bright, but not very hot. Main sequence stars- the hotter the star, the brighter. The sun is an average star and located in the middle of the diagram White dwarfs are very hot but not very bright.

LET’S TRY IT! ACTIVITY: H – R DIAGRAM