S1) Describe, with the aid of a drawing, the main parts of a spiral galaxy like the Milky Way. Where is gas and dust found? Where are globular clusters found? What kind of orbits do halo stars and globular clusters have? What kind of orbits do disk stars have?
S2) In what kinds of gas clouds do you find ionized atoms? In what kinds of gas clouds do you find atoms that are not ionized? In what kinds of gas clouds do you find molecules. Which of these is hottest, which is coolest?
Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA email@example.com