Lecture 33- What’s the Milky Way made of? M74: a Milky Way analog
How is the mass distributed? How could we tell?
Force of Gravity acts on the Sun and all objects in the Galaxy Gravity has magnitude and direction
Sun responds to net force by moving on circular path around the galactic center
Mass distributions like 1,2, and 3 give circular orbits with V(R)
The Observed Case for the Milky Way No sign of the “root-R falloff”
Significance of the Rotation Curve for the Milky Way Rotation curve stays high outside the bulk of the stars Mass indicated by the rotation curve exceeds that in stars Most of the mass of the Milky Way is in an unknown form of “Dark Matter”
The New View of the Milky Way Dadark matter halo
Dark Matter: A Major Problem for Contemporary Physics and Astronomy Stars are a small fraction of the mass of major galaxies The dark matter problem becomes more pronounced as you go out in the universe The form of the dark matter is unknown; probably not what you studied in chemistry Possibly/probably an unknown form of elementary particle