1. Interstellar Medium (ISM) Read Your Textbook: Foundations of Astronomy –Chapter 11, 12 Homework Problems Chapter 11 –Review Questions: 1, 2, 5, 6 –Review Problems: 2-6 –Web Inquiries: 1 Homework Problems Chapter 12 –Review Questions: 2, 3, 8, 9 –Review Problems: 3, 7-9 (old 1, 4-7) –Web Inquiries: 1

2. A Galaxy Rich in Gas and Dust

3. ISM The bright regions are congregations of innumerable stars. However, the dark areas are not simply "holes" in the stellar distribution. They are regions of space where interstellar matter obscures the light from stars beyond. Their very darkness means that they cannot be easily studied by optical methods used for stellar matter. There is, quite simply, very little to see in visible light!

4. Gas and Dust Identical regions of space in the optical and infrared.

5. Nebulosity Star formation regions are rich in gas and dust.

6. Absorption of starlight by the ISM causes interstellar reddening.

7. Extinction Probing the ISM by examining absorption lines in stellar spectra caused by intervening clouds.

8. ISM Characteristics

9. 21-cm Radio Emission

10. 21-cm Radio Energy Transition

11. 21-cm Milky Way

12. ISM Composition Also popular cometary chemical composition list.

13. Gravitational Collapse Star formation begins when gravity begins to dominate over heat, causing a cloud to lose its equilibrium and start to contract. Only after the cloud has undergone radical changes in its internal structure is equilibrium finally restored.

14. Protostar Disk

15. Orion Nursery

16. Star Formation Regions

17. Cloud ShockWave

18. Cloud Fragmentation Star formation usually involves creating “clusters” of stars.

19. Open Cluster Thousands of stars, sometimes gravitationally bound Contain the youngest, hottest galactic stars Associated with star formation regions in the galaxy.

20. Globular Cluster Hundreds of thousands of stars, gravitationally bound and spherically symmetric. Contain the oldest galactic stars Symmetrically distributed about the galaxy.

21. ProtoStar Tracks

22. Protostar Stages

23. Hyashi Tracks

24. Gravity Versus Pressure

25. Stellar Structure Laws