1. Albireo: The Boy Scout star Chapter 5: Binary stars and stellar masses

2. Kepler’s Three Laws of Planetary Motion 1.Planetary orbits are elliptical 2.A planet sweeps out equal areas in equal times 3.P 2 = a 3

3. M1M1 M2M2 r1r1 r2r2 CM Two stars orbit their center of mass

4. M1M1 M2M2 a Make one star the focus of an ellipse

5. Visual binary: not viewed face on

6.  Centauri system (visual binary)

8. Spectroscopic binary

12. MASS-LUMINOSITY RELATION (for MAIN SEQUENCE STARS) L = M  where [L] = L  and [M] = M  Approximately: M < 0.3 M   = 1.8 0.3 M  < M < 3 M   = 3.5 M > 3 M   = 2.8

13. OBSERVEDAPPROXIMATE FITS

18. a1a1 a2a2 M1M1 M2M2