1. February 2, 2012 In our study of Stars The students will be able to
Determine color, temp., brightness
and Size of a star
And show what they learned by
Interpreting the HR Diagram
February 2, 2012

2. WARM-UP

3. Scientists classify stars based on their brightness (Luminosity)
HR DIAGRAM
Hertzsprung-Russel Diagram
Scientists classify stars based on their
brightness (Luminosity)
And
Temperature

4. Classifying Stars Astronomers classify stars according to: size/mass,
temperature,
color, and
brightness.

5. How bright a star or galaxy shines is its brightness or luminosity=
Brightness
How bright a star or galaxy shines is its brightness or luminosity

6. Draw this graph in your journal:
Luminosity (Brightness)
Temperature

7. Notice what happens to the numbers as we move from Left to Right.
Now add your numbers
Along the edge of the
graph
Notice what happens to the numbers as we move from Left to Right.

8. Increasing Temperature
Now add your numbers
Along the edge of the
graph
Increasing Temperature

9. Now add your numbers
Along the edge of the
graph
Hotter
Colder

10. Now let’s look at Luminosity:
Luminosity (Brightness)
Bright
Stars
Increasing
Dim
Stars
Temperature

11. Now let’s begin placing our different types of stars
White Dwarfs
(Dead Stars

12. (Very stable in their life,
Now let’s begin placing our different types of stars
Main Sequence Stars
(Very stable in their life,
Young to middle aged
stars)
White Dwarfs
(Dim Stars)

13. White Dwarfs
(Dim Stars)

14. White Dwarfs (Dim Stars)
Our Sun
White Dwarfs
(Dim Stars)

16. Star Temperatures
Color of a star indicates its surface temperature
Red stars are the ”coolest” while blue are the hottest
Sun is a yellow star

17. Hertzsprung-Russell Diagram17

18. 27.2 The size of stars Stars come in a range of sizes and masses.
Our Sun is a medium-sized star.
The largest stars, giant stars have a mass of about 60 times the mass of the Sun.

22. Which star is hottest supergiant?

23. What temperature is Sirius B?

24. Which star is the dimmest (least bright) on the chart?

25. Order these stars from hottest to coolest:
Procyon, Spica, Sirius B, and Pollux