The document provides an overview of galaxies and the Milky Way galaxy. It discusses that galaxies contain billions of stars and describes our Milky Way galaxy as a spiral galaxy containing 100-200 billion stars. It also discusses other galaxy types like elliptical galaxies and active galaxies like quasars.

1. Astronomy Topic 06 : Galaxies Stephen’s Quintet

5. Milky Way Diagram http://zebu.uoregon.edu/~imamura/123/images/mw-schematic.jpg

6. Milky Way

7. Infrared Milky Way (COBE) http://www.astro.psu.edu/users/niel/astro1/slideshows/class21/slides-21.html The view from within, in IR light

9. Sun’s Revolution http://www.envirotruth.org/images/graphics/suns_path.jpg

11. Milky Way Map http://members.nova.org/~sol/chview/milkyway.jpg

14. Cluster Summary Type Open Cluster Globular Cluster Stars Dozens to thousands (Population I) Hundreds to millions (Population II) Location Within galactic disk Orbit galaxy in halo Age Young, thousands to millions of years Among oldest known stars (billions of years)

16. Open Clusters Pleiades—M45 M67 Which cluster is oldest? Note the star colors of the main stars in each cluster

19. Dark Matter in NGC 3198 http://bustard.phys.nd.edu/Phys171/lectures/ngc3198_opt_rad_rot.jpg

28. Barnard’s S Nebula http://www.astropix.com/HTML/D_SUM_S/B72.HTM A dark nebula represents interstellar dust that blocks the light of stars from behind

29. Horsehead Nebula Famous dark nebula (B33) located near the Belt of Orion

32. Messier Catalog All of the Messier objects are shown in this montage M1 starts the upper left, M110 ends the lower right

37. Andromeda Galaxy (M31, M32, M110)

38. Andromeda Constellation Locate M31 and M33

39. Triangulum Galaxy (M33)

40. M33 The pink glow of emission nebulas can be seen in this photo

42. Center of Virgo Cluster Virgo Cluster near M84, M86 M86

43. Sombrero Galaxy (M104) from HST

45. Large-Scale Structure of the Universe http://www.astro.princeton.edu/~cen/PROJECTS/p1/DARKallz0.jpeg Sheets & Voids: http://heasarc.nasa.gov/docs/cosmic/sheets_voids.html

49. 3C 273-Quasar HST image of 3C 273 showing disk details (quasar blocked) 3C 273 Starfield in Virgo 3C 273 is one of the first identified quasars, it resembles an 11 th magnitude star in Virgo and is visible in small amateur telescopes