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Binary Stars. Double Stars/Binary Stars. Double Star. Earth. Binary Star. Earth. Visual Binary Stars. Center of Mass. Orbit of Star 1. Orbit of Star 2. Sirius A & B. Orbit of 12 Persei (Barlow, Scarfe, and Fekel. Visual Binaries.
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Double Stars/Binary Stars Double Star Earth Binary Star Earth
Visual Binary Stars Center of Mass Orbit of Star 1 Orbit of Star 2
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
Spectroscopic Binaries Spectrum of Hydrogen in Lab Spectrum a Star…..Day 1 Spectrum a Star…..Day 2 Spectrum a Star…..Day 3 Spectrum a Star…..Day 4 What do these spectra tell us about the star?
Radial Velocity Curve HDE 226868
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.
Classifications Detached 65 RT And Semi-detached 203 U Cep Over-Contact 12 XY Leo
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
Second contact separation = difference in radii Eclipse begins separation = sum of radii Relative radius Time difference between these events gives radii of stars