1. Binary Stars

2. Double Stars/Binary Stars Binary Star Double Star Earth

3. Visual Binary Stars Orbit of Star 1 Orbit of Star 2 Center of Mass

4. Sirius A & B

5. Orbit of 12 Persei (Barlow, Scarfe, and Fekel

6. Visual Binaries  Stars must be either close to us or far from each other.  Long orbital periods indicate they are far from each other. (years to decades)  About 10% of all stars are visual binaries  Possible planet detection

7. Spectroscopic Binaries Spectrum of Hydrogen in Lab Spectrum a Star…..Day 1 What do these spectra tell us about the star? Spectrum a Star…..Day 2 Spectrum a Star…..Day 3 Spectrum a Star…..Day 4

8. Spectroscopic Binary Stars

9. Radial Velocity Curve HDE 226868

10. Spectroscopic Binaries  Orbital Periods are several days  Stars are close together  Orbits inclined  90° to sky are discovered this way.  All of the extra-solar planets have been found in this way.

11. Eclipsing Binary Stars

13. Roche Lobes

14. Classifications Detached 65 RT And Semi-detached 203 U Cep Over-Contact 12 XY Leo

15. Star Light Pro

16. Eclipsing Binaries  Chances of finding an eclipsing binary  Inclined  90° to sky  Stars close together  Same conditions as spectroscopic binary  Many are discovered in both ways  Eclipsing binaries also permit radius to be determined

17. Relative radius Eclipse begins separation = sum of radii Second contact separation = difference in radii Time difference between these events gives radii of stars

19. Mass-Luminosity Relationship