ASTR 1102-002 2008 Fall Semester

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# ASTR 1102-002 2008 Fall Semester - PowerPoint PPT Presentation

## ASTR 1102-002 2008 Fall Semester

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##### Presentation Transcript

1. ASTR 1102-0022008 Fall Semester Joel E. Tohline, Alumni Professor Office: 247 Nicholson Hall [Slides from Lecture03]

2. University-wide, Gustav-motivated Calendar Modifications

3. University-wide, Gustav-motivated Calendar Modifications

4. Gustav’s Effect on this Course • Fall Holiday has been cancelled, which means our class will meet on Thursday, 9 October. (This makes up for one class day lost to Gustav last week.) • We will hold an additional makeup class on Saturday, 20 September! (This will account for the second class day lost to Gustav last week.) • Date of Exam #1 has been changed to Tuesday, 23 September!

5. Course Syllabus

6. Course Syllabus

7. Chapter 17: The Nature of Stars

8. Describe a Population of Stars

9. Individual Stars… • Location in Space • Coordinate (angular) position on the sky [Right ascension & Declination] • Distance from Earth [use Stellar Parallax] • Motion through Space • Motion across the sky [“proper” motion] • Motion toward/away from us (radial velocity) [use Doppler Effect]

11. Stellar Parallax (§17-1) • Understand Figs. 17-1, 17-2, and eyes+thumb illustrations. • Star ‘A’ exhibits a stellar parallax that is twice as large as the stellar parallax exhibited by star ‘B’. • Which star is farther from us? • How much farther away? • If parallax angle (p) is measured in arcseconds and distance is measured in ‘parsecs’ (see §1-7 and Fig. 1-14), then ... • d = 1/p

12. Stellar Parallax (§17-1) • Understand Figs. 17-1, 17-2, and eyes+thumb illustrations. • Star ‘A’ exhibits a stellar parallax that is twice as large as the stellar parallax exhibited by star ‘B’. • Which star is farther from us? • How much farther away? • If parallax angle (p) is measured in arcseconds and distance is measured in ‘parsecs’ (see §1-7 and Fig. 1-14), then ... • d = 1/p

13. March sky image

14. September sky image

15. Stellar Parallax (§17-1) • Understand Figs. 17-1, 17-2, and eyes+thumb illustrations. • Star ‘A’ exhibits a stellar parallax that is twice as large as the stellar parallax exhibited by star ‘B’. • Which star is farther from us? • How much farther away? • If parallax angle (p) is measured in ‘arcseconds’ and distance is measured in ‘parsecs’ (see §1-7 and Fig. 1-14), then ... • d = 1/p

16. Individual Stars… • Location in Space • Coordinate (angular) position on the sky [Right ascension & Declination] • Distance from Earth [use Stellar Parallax] • Motion through Space • Motion across the sky [“proper” motion] • Motion toward/away from us (radial velocity) [use Doppler Effect; §5-9]

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

18. Prominent and Obscured Objects

19. Prominent and Obscured Objects

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

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

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

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

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

25. 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

26. Stars of different brightness

27. Stars of different colors

28. Apparent brightness due to… • Each star’s intrinsic brightness • Each star’s distance from us

29. Apparent Brightness varies with Distance

30. Color-Temperature Relationship

31. More About: Continuous Spectra from Hot Dense Gases (or Solids) • Kirchhoff’s 1st Law: Hot dense gas produces a continuous spectrum (a complete rainbow of colors) • A plot of light intensity versus wavelength always has the same general appearance (blackbody function): • Very little light at very short wavelengths • Very little light at very long wavelengths • Intensity of light peaks at some intermediate wavelength • But the color that marks the brightest intensity varies with gas temperature: • Hot objects are “bluer” • Cold objects are “redder”

32. The Sun’s Continuous Spectrum (Textbook Figure 5-12)

33. Wien’s Law for Blackbody Spectra • As the textbook points out (§5-4), there is a mathematical equation that shows precisely how the wavelength (color) of maximum intensity varies with gas temperature.