1. Lecture 29 – An advertisement: two astronomy courses next semester 29:52,“Characteristics and Origins of the Solar System, 1:30 – 2:20 MWF 143:070:001, Honors Seminar in Natural Sciences, “Life in the Universe: Scientific Bases for Speculation”, 2:30- 3:45 TTh

2. Why study the solar system next semester? Jupiter, Saturn, and Venus will all be in the evening sky

3. Astronomical Events this Month Venus in the western sky after sunset Total eclipse of the Moon, November 8 (Saturday night) 5:32 PM 7:06 7:31 9:04 Leonid meteor shower, November 18, before dawn

4. Last word on massive stellar evolution: it happens fast and ends violently Eta Carinae: Watch the skies! Watch the skies!

5. Next topic: Structure of the Milky Way Galaxy What is the size, shape, and nature of the system of stars in which we live?

6. You can learn a lot by looking at the sky and thinking

7. From this picture, let’s figure out the shape of the Milky Way. Characteristics to go on are: Sprinkling of stars everywhere Thick band of light across the sky (the Milky Way) Band brightest in the direction of Sagittarius Band faintest in the direction of Taurus- Auriga What’s the answer?

8. The Answer

10. How far is it to the galactic center? How could we know? Hint provided by globular star clusters. Great summertime objects, few in winter

11. How globulars indicate the distance to the galactic center

12. Globular Clusters are Distant It must be a long way to the galactic center Globular clusterDistance (light years) M13 (Hercules)21,000 M15 (Aquarius)34,000 M92 (Hercules)26,000 M4 (Scorpius)14,000 M5 (Serpens)26,000