1. Agenda: galaxies The Milky Way Types of galaxies Finding distances to galaxies

2. Activity grades Missing group numbers will result in lost points. Signatures will be required to receive credit. There are lots of unclaimed assignments—check my folder! WebCT grades are updated after each exam.

3. Hydrogen Gas CO: Molecular Clouds Interstellar Dust hot gas bubbles Stars: no blocking Seeing the Milky Way

4. NASA Is it like this?

5. AATB Or this?

6. NOAO Or this?

7. What we see:

8. Another galaxy… NASA

9. Compare

10. Compare to this one

11. Harlow Shapley (1885-1972) Looked at many globular clusters Determined their distance from us We are not at the center of the galaxy!

12. We live in a spiral galaxy! Globular clusters Our galaxy is centered about here Stars we can see Our solar system

13. Shape of our galaxy ESA

14. Our black hole CHANDRA Crazy x-ray bursts!

15. Our black hole NRAO Radio waves

16. Hubble rocks!!! Edwin Hubble 1889-1953

17. Our neighbor Andromeda R. Gendler

18. Spiral galaxy

19. Spiral galaxy on edge NOAO Dusty!!

20. Barred Spiral Spiral arms start at the end of the bar. hubble space telescope

21. Caltech Types of spiral galaxies

22. Types of barred spiral galaxies Caltech

23. David Malin Elliptical galaxy Globular clusters Contain mainly older stars

24. Types of elliptical galaxies Rotation not uniform Caltech

25. NOAO Irregular galaxy

26. Irregular galaxy Some galaxies have asymmetric shapes, often because they are interacting with their neighbors. HST NGC4676, the “mice”

27. Consider Hubble’s hypothesis: Do galaxies evolve from elliptical to spiral? A. YesB. NoC. Cannot conclude Increasing age?

28. Do galaxies evolve? Ellipticals contain mainly older stars Spirals contain much dust and gas Increasing age?

29. Calculating distances to other galaxies Cepheid variables Type I supernovae Hubble’s law

30. Cepheid variables Gene Smith, UCSD/CASS Cepheids are a standard candle. Discovered by Henrietta Leavitt. (photo: AAVSO)

31. Harvard Supernovae in 4 galaxies All Type I supernovae reach same maximum luminosity. Another standard candle!

32. Summary Our galaxy—the Milky Way  Spiral shape (mapped using clusters)!  We have our own black hole! Galaxies classified by Hubble  Elliptical  Spiral  Barred spiral  Irregular Measuring distance to galaxies  Cepheid variable stars  Type I supernovae

33. Team activity #8 Stellar evolution Make sure you label all LINES!