1. A Spiral Nebula as a Stellar System, Messier 31 By Edwin Hubble

2. Not So Easy Astronomy

3. Cepheid Light Curves

4. Period Luminosity Relationship

5. Extra Galactic Cepheids

6. Light Curves of Novae

7. Nova and Cepheid Frequency Distribution

8. Distribution of Novae

9. Conclusions Hubble Found… Found distance of M31 to be 275 kpc Found the total mass to be 2.4*10^8 solar masses Today We Find… Stanek and Garnavich 1998 found the distance to be ~780kpc Wilkinson and Evans 2000 found the total mass to be 1.2*10^12 solar masses