ASTR 1102-002 2008 Fall Semester

1. ASTR 1102-0022008 Fall Semester Joel E. Tohline, Alumni Professor Office: 247 Nicholson Hall [Slides from Lecture02]

2. Course Syllabus(corrected Final Exam time!)

3. Evaluation of Coursework Corrected final exam time!

4. Chapter 17: The Nature of Stars

5. Describe Population (of stars) • Location • Coordinate position • Distance • Motion • Across the photo/sky • Toward/away from us • Intrinsic properties • Mass • Color • Brightness • Age

6. Describe Population (of fans) • Location • Coordinate position • Distance • Motion • Across the photo/sky • Toward/away from us • Intrinsic properties • Mass (weight) • Color (clothes) • Brightness (?) • Age

8. Location – Determine exact location of every fan! • Coordinate position • Distance

9. Location – Determine exact location of every fan! • Coordinate position (x-y coordinate on photo) • Distance (distance from photographic lens)

10. Location – Determine exact location of every fan • Coordinate position (x-y coordinate on photo) straightforward • Distance (distance from photographic lens)

11. Location – Determine exact location of every fan • Coordinate position (x-y coordinate on photo) • Distance (distance from photographic lens) not so straightforward!

12. e.g., Google Earth • Location – or … using GPS system … • Coordinate position (latitude & longitude) • Distance (altitude above sea level)

13. Google Earth

14. Location – Determine exact location of every star! • Coordinate position • Distance

15. Location – Determine exact location of every star! • Coordinate position (“declination” & “right ascension”) • Distance (from Earth)

16. Straightforward: Analogous to “latitude” & “longitude”; e.g., Google Sky Textbook ‘Box 2-1’ pp. 30-31 • Location – Determine exact location of every star! • Coordinate position (“declination” & “right ascension”) • Distance (from Earth)

17. Google Sky

18. Location – Determine exact location of every star! • Coordinate position (“declination” & “right ascension”) • Distance (from Earth) not so straightforward!

19. Determining Distances to Astronomical Objects • Not at all straightforward! • Only direct method is “Stellar Parallax” • See textbook discussion associated with Figs. 17-1 and 17-2 • Other indirect methods will be discussed later

20. Parallax

21. Stellar Parallax

22. Individual Stars… • Location in Space • Coordinate (angular) position on the sky • Distance from Earth • Motion through Space • Motion across the sky (“proper” motion) • Motion toward/away from us (radial velocity) • Intrinsic properties • Brightness (luminosity/magnitude) • Color (surface temperature) • Mass • Age

23. Individual Stars… • Location in Space • Coordinate (angular) position on the sky • Distance from Earth • Motion through Space • Motion across the sky (“proper” motion) • Motion toward/away from us (radial velocity) • Intrinsic properties • Brightness (luminosity/magnitude) • Color (surface temperature) • Mass • Age

24. Motion • Across the photo/sky • Toward/away from us • Location • Coordinate position • Distance

25. Motion • Across the photo/sky • Toward/away from us • Location • Coordinate position • Distance

26. Motion • Across the photo/sky • Toward/away from us • Location • Coordinate position • Distance

27. Which object in this photo is moving?

28. Motion Across the Sky(“proper” motion) http://www.psi.edu/~esquerdo/jim/astfov.gif

29. Motion • Across the photo/sky • Toward/away from us • Location • Coordinate position • Distance

30. Determining Motion of Astronomical Objects toward/away • Surprisingly straightforward! • Doppler effect • See textbook discussion in Chapter 5, §5-9

31. Doppler Effect (§5-9) • The measured frequency (wavelength) of light changes if the light source is moving toward or away from you • Light is “blue-shifted” if the object is moving toward you • Light is “red-shifted” if the object is moving away from you • Direct analogy with the behavior of sound waves

33. Individual Stars… • Location in Space • Coordinate (angular) position on the sky • Distance from Earth • Motion through Space • Motion across the sky (“proper” motion) • Motion toward/away from us (radial velocity) • Intrinsic properties • Brightness (luminosity/magnitude) • Color (surface temperature) • Mass • Age

34. Prominent and Obscured Objects

35. Prominent and Obscured Objects

36. NOTE: Transient Events (in time) also occur

37. NOTE: Transient Events (in time) also occur

38. NOTE: Transient Events (in time) also occur

39. NOTE: Transient Events (in time) also occur

40. NOTE: Transient Events (in time) also occur

41. Individual Stars… • Location in Space • Coordinate (angular) position on the sky • Distance from Earth • Motion through Space • Motion across the sky (“proper” motion) • Motion toward/away from us (radial velocity) • Intrinsic properties • Brightness (luminosity/magnitude) • Color (surface temperature) • Mass • Age