Binary Stars

Double Stars/Binary Stars

Binary Star

Double StarEarth

Earth

Visual Binary Stars

Orbit of Star 1

Orbit of Star 2

Center of Mass

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 binariesPossible planet detection

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

Spectroscopic Binary Stars

Radial Velocity Curve

HDE 226868

Spectroscopic Binaries

Orbital Periods are several daysStars are close together

Orbits inclined 90° to sky are discovered this way.

All of the extra-solar planets have been found in this way.

Eclipsing Binary Stars

Roche Lobes

Classifications

Detached65 RT And

Semi-detached203 U Cep

Over-Contact12 XY Leo

Star Light Pro

Eclipsing Binaries

Chances of finding an eclipsing binaryInclined 90° to skyStars close together

Same conditions as spectroscopic binaryMany are discovered in both ways

Eclipsing binaries also permit radius to be determined

Relative radius

Eclipse beginsseparation = sum of radii

Second contactseparation = difference in radii

Time difference between these events gives radii of stars

Mass-Luminosity Relationship