1. Stars and Galaxies

2. What are we going to cover?  Our Place in the Universe  The Electromagnetic Spectrum  Classifying Stars  Classifying Galaxies  History of the Universe

3. First up…  Our Place in the Universe  What is our Universe made of?  How big are things? How far away?  How do we know?

4. Examining the Components  Stars  Gas and dust (Nebulae)  Star clusters  Galaxies

6. Different types of stars Image from http://hubblesite.org/newscenter/archive/releases/star%20cluster/globular/2003/21/image/a/results/50/ http://hubblesite.org/newscenter/archive/releases/star%20cluster/globular/2003/21/image/a/results/50/

7. Types of Stars  Big (Super massive)  Small (Dwarf)  Red  Blue  Yellow  In groups (Clusters)  Alone (Rogue)  More later

8. What is a “star cluster”?   stars formed together at same time   stars may be gravitationally bound together   two types: open (galactic) and globular Image at http://hubblesite.org/newscenter/archive/releases/star%20cluster/globular/2007/18/image/a/format/web/results/50/ http://hubblesite.org/newscenter/archive/releases/star%20cluster/globular/2007/18/image/a/format/web/results/50/

9. Open Clusters   dozens to thousands of stars   young stars! only a few million years old   may still be surrounded by nebula from which they formed   located in the spiral arms of a galaxy   example: Pleiades Image at http://hubblesite.org/newscenter/archive/releases/star%20cluster/open/2004/20/image/a/results/50/http://hubblesite.org/newscenter/archive/releases/star%20cluster/open/2004/20/image/a/results/50/

10. More open star clusters Image from http://hubblesite.org/newscenter/archive/releases/star%20cluster/open/2006/17/image/a/results/50/http://hubblesite.org/newscenter/archive/releases/star%20cluster/open/2006/17/image/a/results/50/

11. Globular Clusters   millions to hundreds of millions of stars   old! 6 to 13 billion years   mostly red giants and dwarfs   stars are clumped closely together, especially near the center of the cluster (densely)   surround our disk as a halo Image at http://hubblesite.org/newscenter/archive/releases/star%20cluster/globular/1999/26/image/a/results/50/ http://hubblesite.org/newscenter/archive/releases/star%20cluster/globular/1999/26/image/a/results/50/

12. What is a “nebula”?  A cloud in space  Made of gas and dust   Can have stars inside  Most of the ones we see are inside our Milky Way Galaxy  Different types Orion image at http://hubblesite.org/newscenter/archive/releases/2006/01/image/a/results/50/http://hubblesite.org/newscenter/archive/releases/2006/01/image/a/results/50/

13. Large, massive, bright nebulae Emission Nebula The hot gas is emitting lightThe hot gas is emitting light Orion image at http://hubblesite.org/newscenter/archive/releases/2006/01/image/a/results/50/http://hubblesite.org/newscenter/archive/releases/2006/01/image/a/results/50/

14. Colder, darker nebulae Dark dust blocking the hot gas behind it NOAO/AURA/NSF Image from http://hubblesite.org/newscenter/archive/releases/nebula/dark/2001/12/image/c/results/50/ http://hubblesite.org/newscenter/archive/releases/nebula/dark/2001/12/image/c/results/50/

15. Leftovers from an Explosion Supernova remnant (smaller, less gas) Image at http://hubblesite.org/newscenter/archive/releases/nebula/supernova-remnant/2005/37/results/50/http://hubblesite.org/newscenter/archive/releases/nebula/supernova-remnant/2005/37/results/50/

16. What is a “galaxy”?  A large group of stars outside of our own Milky Way  Made of billions to trillions of stars  Also may have gas and dust  Spiral, or elliptical, or irregular shaped Image at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2007/41/results/50/http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2007/41/results/50/

17. Spiral galaxy--Andromeda NOAO/AURA/NSF Images at http://www.noao.edu/image_gallery/html/im0606.html and http://www.noao.edu/image_gallery/html/im0685.htmlhttp://www.noao.edu/image_gallery/html/im0606.html http://www.noao.edu/image_gallery/html/im0685.html

18. Elliptical Galaxies Images at http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/2007/08/image/a/format/large_web/results/50/ and http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/1995/07/results/50/http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/2007/08/image/a/format/large_web/results/50/http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/1995/07/results/50/

19. Irregular Galaxies NASA and NOAO/AURA/NSF Images at http://hubblesite.org/newscenter/archive/releases/galaxy/irregular/2005/09/results/50/, http://www.noao.edu/image_gallery/html/im0560.html, and http://www.noao.edu/image_gallery/html/im0993.html http://hubblesite.org/newscenter/archive/releases/galaxy/irregular/2005/09/results/50/ http://www.noao.edu/image_gallery/html/im0560.htmlhttp://www.noao.edu/image_gallery/html/im0993.html

20. 20 How big is the Milky Way Galaxy? 100,000 light years Image credits: NASA, STScI

21. Our Galaxy: the Milky Way   has about 200 billion stars, and lots of gas and dust   is a barred-spiral (we think)   about 100,000 light-years wide   our Sun is halfway to the edge, revolving at half a million miles per hour around the center of the Galaxy   takes our Solar System about 200 million years to revolve once around our galaxy

22. The Milky Way Image at http://news.nationalgeographic.com/news/bigphotos/1945371.htmlhttp://news.nationalgeographic.com/news/bigphotos/1945371.html

23. Mapping the Milky Way We can see stars  star clusters  nebulae  Galaxies  Let’s try to Map our Galaxy How do we know what our Galaxy looks like?

24. Measuring Distances  What is a Light Year?  A light year is the distance light travels in a year. Light moves at a velocity of about 300,000 kilometers (km) each second; how far would it move in a year?  About 10 trillion km (or about 6 trillion miles).  Why do we use light years?  Show me how far 5 centimeters is.  Now show me 50 centimeters.  Now tell me (without thinking about it, or calculating it in meters) how far 500 centemeters is. 2000? 20,000?  We need numbers that make sense to us in relationship to objects; we scale up and use meters and kilometers for large numbers.