1. Chapter 15 Surveying the Stars

2. 15.2 Patterns Among Stars

3. Temperature Luminosity An H-R diagram plots the luminosity and temperature of stars

4. Temperature Luminosity H-R diagram depicts: Temperature Color Spectral Type Luminosity Radius

5. 90 % of stars fall somewhere on the main sequence of the H-R diagram – these stars are fusing hydrogen into helium

6. Luminous main- sequence stars are hot (blue) Less luminous ones are cooler (yellow or red)

7. Mass measurements of main-sequence stars show that the hot, blue stars are much more massive than the cool, red ones High-mass stars Low-mass stars

8. The mass of a normal, hydrogen- burning star determines its luminosity and spectral type! High-mass stars Low-mass stars

9. Stars with lower T and higher L than main- sequence stars must have larger radii: giants and supergiants Large radius

10. Small radius Stars with higher T and lower L than main- sequence stars must have smaller radii: white dwarfs

11. A star’s full classification includes spectral type (line identities) and luminosity class (line shapes, related to the size of the star): I - supergiant II - bright giant III - giant IV - subgiant V - main sequence Examples:Sun - G2 V Sirius - A1 V Proxima Centauri - M5.5 V Betelgeuse - M2 I

12. Stellar Properties Review Luminosity: from brightness and distance 10 -4 L Sun - 10 6 L Sun Temperature: from color and spectral type 3,000 K - 50,000 K Mass: from period (p) and average separation (a) of binary-star orbit 0.08 M Sun - 100 M Sun

13. Stellar Properties Review Luminosity: from brightness and distance 10 -4 L Sun - 10 6 L Sun Temperature: from color and spectral type 3,000 K - 50,000 K Mass: from period (p) and average separation (a) of binary-star orbit 0.08 M Sun - 100 M Sun (0.08 M Sun ) (100 M Sun ) (0.08 M Sun )

14. Mass & Lifetime A star’s life expectancy depends on its mass and its luminosity. Mass determines how much hydrogen it has to begin with luminosity determines how fast the hydrogen is burned. Sun’s life expectancy: 10 billion years

15. Mass & Lifetime A star’s life expectancy depends on its mass and its luminosity. Mass determines how much hydrogen it has to begin with luminosity determines how fast the hydrogen is burned. Sun’s life expectancy: 10 billion years Until core hydrogen (10% of total) is used up

16. Mass & Lifetime A star’s life expectancy depends on its mass and its luminosity. Mass determines how much hydrogen it has to begin with luminosity determines how fast the hydrogen is burned. Sun’s life expectancy: 10 billion years Life expectancy of 10 M Sun star: 10 million years 10 times as much fuel, uses it 10 4 times as fast lifetime is only 1/1000 as long as the sun’s Until core hydrogen (10% of total) is used up

17. Mass & Lifetime Sun’s life expectancy: 10 billion years Life expectancy of 10 M Sun star: 10 million years 10 times as much fuel, uses it 10 4 times as fast lifetime is only 1/1000 as long as the sun’s Life expectancy of 0.1 M Sun star: 100 billion years 0.1 times as much fuel, uses it 0.01 times as fast lifetime is 10 times longer than the sun’s Until core hydrogen (10% of total) is used up

18. Main-Sequence Star Summary High Mass: High Luminosity Short-Lived Large Radius Blue Low Mass: Low Luminosity Long-Lived Small Radius Red

19. What are giants, supergiants, and white dwarfs?

20. Off the Main Sequence Stellar properties depend on both mass and age: those that have finished fusing H to He in their cores are no longer on the main sequence All stars become larger and redder after exhausting their core hydrogen: giants and supergiants Most stars end up small and white after fusion has ceased: white dwarfs

22. A1VK0 IIIb K0 III

23. 0 B8 I K5 III M1.5 IM2 I