1. Lecture 23- Interstellar Chemistry and Life After the Main Sequence Chemistry = (defined) as interaction of two (or more) molecules to form different molecules

2. Interstellar Chemistry How complicated does it get? H 2, CO, H 2 O, NH 3

3. Our window on interstellar chemistry: microwave spectroscopy Each molecule has a unique “fingerprint” set of frequencies

4. Example of an interstellar molecule Interstellar Acetic Acid, CH 3 COOH

5. Notice other emission lines not identified

6. Current State of Astrochemistry Table of detected molecules > 110 molecules found in interstellar space The largest contain up to 13 atoms Many, if not most, are organic Nobody doubts there are more complicated species lurking out there (unidentified lines) Connection to the origin of life?

7. Next Topic: The Other Side of the Main Sequence. All stars in a cluster formed at the same time

8. Look at the HR diagram of a cluster What can you say?

9. Post-Main Sequence Stellar Evolution: Example Betelgeuse Lesson 1- Stars get bloated and red

10. Post-Main Sequence Stellar Evolution The course of evolution depends on mass High Mass stellar evolution Low Mass stellar evolution The two kinds of evolution are quite similar for a while, then wildly diverge

11. A star at the end of its Main Sequence Lifetime No fuel source to keep up the central pressure. The core begins to contract under its own gravity

12. Contraction continues until proton-proton cycle begins in shell around the core Calculations show that outer layers of star swell up to form a red giant