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The Milky Way Structure of the Milky Way The Milky Way Components of the Milky Way Disk Population I stars Open clusters HII regions Bulge Population II stars Halo Globular clusters Omega Centauri Stellar Populations M100 Finding Our Place Globular Clusters evenly distributed
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Components of the Milky Way • Disk • Population I stars • Open clusters • HII regions • Bulge • Population II stars • Halo • Globular clusters
Stellar Populations M100
Finding Our Place Globular Clusters evenly distributed Early view Sun at center Sun Globular Clusters unevenly distributed Harlow Shapley
Mapping the Galaxy • Visible Light • Strong interstellar absorption • We can see only 4000 - 5000 pcs • Radio Light • Can observe entire galaxy
21-cm Radiation Electron Proton
Wavelength Mapping the Galaxy • H clouds in different spiral arms will have different Doppler Shifts Sun
Observed Rotation Curve Keplerian Orbits
Dark Matter • There must be significant amount of mass in the Galaxy in an underluminous form (perhaps as much as 90% of total) • Compact Objects - White Dwarf, Neutron Stars, Black Holes • MACHO’s - MAssive Compact Halo Objects • Planets, Brown Dwarfs • WIMP’s • Weakly Interacting Massive Particles