1. Classifying Stars

2. Stars are classified by size, temperature, color, and brightness
Classifying Stars
Stars are classified by size, temperature, color, and brightness

3. Star Size
 Stars vary in size from small dwarf stars to very large supergiants
Star size is controlled by density
Density is the amount of matter in a defined amount of space. Density = mass / volume
Dwarf stars are very dense while Supergiants are less dense than our atmosphere

4. Color and Temperature
The color of stars tells us about the star’s temperature.
Blue stars – Hottest C+
White –30000C
Yellow – Medium 5000 – 7500
Orange – 5000
Red stars- Coolest under 3500
Our sun is a yellow star

5. Brightness
Brightness depends on a star’s temperature, size, and distance from us.
Brightest stars:
Blue & white stars, Supergiant & giant stars, and stars that are close to us.

6. Magnitude Magnitude means Brightness
Apparent Magnitude – What we see – mainly depends on distance from us
Absolute Magnitude – What it is – depends on temperature and size
The absolute magnitude of our sun is average, the apparent magnitude of our sun is the largest of any object in our sky.

7. HR Diagram
Hertsprung and Russell came up with a chart that relates a star’s brightness to its color and temperature.
Three main categories:
Main Sequence – contains most stars, found along the diagonal in the chart
Supergiants & Giants – found at the top.
Dwarf stars – found along the bottom.
Our sun is a main sequence star

9. Parts of the HR Diagram
X axis –shows temperature of the star and the color
Temperature increases as it moves to the LEFT
Temperature decreases as it moves to the RIGHT
Star color goes from Blue-white (left) to Yellow to Red (right)

10. Parts of the HR Diagram
Y axis – Shows the true brightness and size of a star
Brightness increases as you move up the diagram
Size increases as you move up the diagram

13. Dwarf stars are found at the bottom of the diagram. Dwarf means small.

14. Dwarf stars are found at the bottom of the diagram. Dwarf means small.

15. Supergiants and Giants are found at the top of the diagram
Supergiants and Giants are found at the top of the diagram. Giant means big.
Dwarf stars are found at the bottom of the diagram. Dwarf means small.

16. Supergiants and Giants are found at the top of the diagram
Supergiants and Giants are found at the top of the diagram. Giant means big.
Main Sequence stars are found on a descending diagonal line on the diagram.
Dwarf stars are found at the bottom of the diagram. Dwarf means small.

17. Supergiants and Giants are found at the top of the diagram
Supergiants and Giants are found at the top of the diagram. Giant means big.
Main Sequence stars are found on a descending diagonal line on the diagram.
Dwarf stars are found at the bottom of the diagram. Dwarf means small.

18. Supergiants and Giants are found at the top of the diagram
Supergiants and Giants are found at the top of the diagram. Giant means big.
Main Sequence stars are found on a descending diagonal line on the diagram.
Dwarf stars are found at the bottom of the diagram. Dwarf means small.

20. HR Diagram
Dwarf stars are found at the bottom of the diagram. Dwarf means small.
Name an example of a white dwarf star on your diagram

21. HR Diagram
Dwarf stars are found at the bottom of the diagram. Dwarf means small.
Name an example of a white dwarf star on your diagram

22. HR Diagram
Dwarf stars are found at the bottom of the diagram. Dwarf means small.
Name an example of a white dwarf star on your diagram

23. HR Diagram
Supergiants and Giants are found at the top of the diagram. Giant means big.
Name an example of a Red Supergiant found on your diagram.

24. HR Diagram
Supergiants and Giants are found at the top of the diagram. Giant means big.
Name an example of a Red Supergiant found on your diagram.

25. HR Diagram
Main Sequence stars are found on a descending diagonal line on the diagram.
Name a super-hot main sequence star from your diagram.

26. HR Diagram
Main Sequence stars are found on a descending diagonal line on the diagram.
Name a super-hot main sequence star from your diagram.

28. HR Diagram
Main Sequence stars are found on a descending diagonal line on the diagram.
Name a ordinary yellow main sequence star from your diagram.