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Binary Stars
Double Stars/Binary Stars
Double Star
Binary Star
Visual Binary Stars
Orbit of Star 1
Center of Mass
Orbit of Star 2
Sirius A & B
Orbit of 12 Persei
(Barlow, Scarfe, and Fekel
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?
Spectroscopic Binary Stars
Radial Velocity Curve
HDE 226868
Spectroscopic Binaries
 Orbital
 Stars
Periods are several days
are close together
inclined 90° to sky are discovered
this way.
 All of the extra-solar planets have been
found in this way.
 Orbits
Eclipsing Binary Stars
Roche Lobes
65 RT And
203 U Cep
12 XY Leo
Star Light Pro
Eclipsing Binaries
 Chances
of finding an eclipsing binary
 90° to sky
 Stars close together
 Inclined
 Same
conditions as spectroscopic binary
 Many
are discovered in both ways
 Eclipsing
binaries also permit radius to be
Relative radius
Eclipse begins
separation = sum of radii
Second contact
separation = difference in radii
Time difference between these
events gives radii of stars
Mass-Luminosity Relationship