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 Sun Early view Sun at center Harlow Shapley Globular Clusters evenly distributed Globular Clusters unevenly distributed

Mapping the Galaxy Visible Light  Strong interstellar absorption  We can see only pcs Radio Light  Can observe entire galaxy

21-cm Radiation Proton Electron

Mapping the Galaxy H clouds in different spiral arms will have different Doppler Shifts Sun Wavelength

21-cm Data

Galactic Rotation Curve

Observed Rotation Curve Keplerian Orbits

Dark Matter Halo

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 qMACHO’s - MAssive Compact Halo Objects  Planets, Brown Dwarfs  WIMP’s qWeakly Interacting Massive Particles