Presentation on theme: "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,"— Presentation transcript:
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 known 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.