1. The Age of Things: Sticks, Stones and the Universe Colors, Brightness, and the Age of Stars http://cfcp.uchicago.edu/~mmhedman/compton1.html

2. WARNING! (Radio) Astrophysict talking about Astronomy!

3. The Brightness of Stars Pollux Castor The Pleades Sirius Sirius B Luminosity = Total power emitted by star in the form of light.

4. 400 nm500 nm 600 nm700 nm Visible Colors and Spectra Wavelength 1 m1 km1 mm 1  m 1 nm1 pm Alberio

5. The Spectra of Stars Wavelength Brightness

6. Thermal Radiation

7. Thermal Spectrum

8. Astronomical Filters

9. Magnitudes Magnitude 0 Magnitude 2 Magnitude 3 2.5 times brighter Arcturus Polaris Magnitude 1 2.5 times brighter Spica

10. Colors Rigel, B-V = - 0.03 Betelgeuse, B-V = 1.85

11. Measuring Distance to the stars using Parallax Earth Sun Background Stars Nearby Stars

12. Magnitudes Magnitude 0 Magnitude 2 Magnitude 3 Arcturus Polaris Magnitude 1 Spica 37 Light years Away 262 Light Years Away 431 Light Years Away

13. Magnitudes Magnitude 0 Magnitude 2 Magnitude 3 Arcturus Polaris Absolute Magnitude - 3.55 Absolute Magnitude - 3.59 Magnitude 1 Spica Absolute Magnitude - 0.30 37 Light years Away 262 Light Years Away 431 Light Years Away

14. Color-Magnitude Diagram Nearby stars (data from the Hipparcos satellite) Absolute Magnitude Color More Luminous Less Luminous BlueRed

15. Globular Clusters M15 NGC 362

16. Color-Magnitude Diagrams of Globular Clusters Nearby StarsGlobular Cluster M13

17. Another Globular Cluster: M15

18. Proton Deuterium Positron Neutrino Positron Neutrino Photon Helium-3 Helium-4 Nuclear Fusion

19. Gravity Fusion Equilibrium in Main Sequence Stars

20. Gravity Fusion Equilibrium in Main Sequence Stars

21. Gravity Fusion Equilibrium in Main Sequence Stars

22. Gravity Fusion Equilibrium in Main Sequence Stars

23. Gravity Fusion Equilibrium in Main Sequence Stars

24. Supporting the Mass of the Star Mass = MMass = 2M 2 times as much material to support

25. Supporting the Mass of the Star Mass = MMass = 2M 2 times as much material to support 2 times the gravitational force on each particle

26. Supporting the Mass of the Star Mass = MMass = 2M 2 times as much material to support 2 times the gravitational force on each particle 2-4 times more rapid rate of energy transport, loss through surface.

27. Supporting the Mass of the Star Mass = MMass = 2M 2 times as much material to support 2 times the gravitational force on each particle 2-4 times more rapid rate of energy transport, loss through surface. Luminosity = LLuminosity ~ 10 L

28. Mass Estimates from Binary stars Mizar 1 70 Ophiuci

29. Mass-Luminosity Relation 1,000,000 10,000 100 1 0.01

30. Mass-Luminosity Relation 1,000,000 10,000 100 1 0.01

31. Main Sequence Lifetimes 1,000,000 10,000 100 1 0.01 Total number of Hydrogen atoms Rate that Hydrogen atoms convert into Helium atoms Time to convert all Hydrogen to Helium 150 billion years

32. Lifetime of a Main Sequence Star Luminosity = 4 * 10 26 Watts 1.5 * 10 17 kilograms/ Year Mass = 2 * 10 30 kilogram All Hydrogen would be converted to Helium in 150 billion years

33. The Schonberg-Chandrasekhar Limit A main-sequence star cannot maintain equilibrium if more than 10% of its total mass has been converted into Helium He H Fusing H HeliumHydrogen Helium has 4 times more mass than Hydrogen Helium undergoes fusion at much higher temperatures than Hydrogen H + H  D D + H  He 3 He 3 + He 3  He 4 He + He + He  C As Helium accumulates in the core, it becomes more and more difficult to support

34. Different Stars, Different Lifetimes Luminosity = L Mass = M Lifetime = 10 Billion Years Luminosity ~ 10 L Mass = 2M Lifetime = 2 Billion Years

35. Main Sequence Lifetimes 1,000,000 10,000 100 1 0.01 Total number of Hydrogen atoms Rate that Hydrogen atoms convert into Helium atoms Time to convert 10% of the Hydrogen to Helium 10 billion years

36. Main Sequence Lifetimes 1,000,000 10,000 100 1 0.01 Time to convert 10% of the Hydrogen to Helium 10 billion years Time to convert 10% of the Hydrogen to Helium 2 billion years

37. The Changing Main Sequence Time = 0 Billion Years

38. The Changing Main Sequence Time = 1 Billion Years

39. The Changing Main Sequence Time = 4 Billion Years

40. The Changing Main Sequence Time = 13 Billion Years

41. Measuring the Age of Globular Clusters

43. V 10 Billion Years 20 Billion Years 12 Billion Years 15 Billion Years M13 M15 B - V The Challenge of Measuring Globular Cluster Ages

44. The Oldest Globular Clusters M68M92M30 M13 NGC362NGC6752 11.5  1.3 billion years 12  1 billion years 11.8  1.2 billion years 14.0  1.2 billion years 12  1 billion years 12.2  1.8 billion years Multiple analyses yield ages of 12 billion years, and an uncertainty of about 1 or 2 billion years Other methods yield similar ages

45. Next Time The Age of the Universe