Changes

By measuring the position angle of the companion star relative to the primary and the angler distance between the two stars over time, the [[ellipse]], called the apparent ellipse, which is the orbit of the secondary in respect to the primary, can be plotted out.  From this measurement of the semi-major axis and orbital period of binary stars' orbit, the mass of the stars can be determined.<ref>http://csep10.phys.utk.edu/astr162/lect/binaries/visual.html</ref>

By measuring the position angle of the companion star relative to the primary and the angler distance between the two stars over time, the [[ellipse]], called the apparent ellipse, which is the orbit of the secondary in respect to the primary, can be plotted out.  From this measurement of the semi-major axis and orbital period of binary stars' orbit, the mass of the stars can be determined.<ref>http://csep10.phys.utk.edu/astr162/lect/binaries/visual.html</ref>

Visual binaries are quite common and in fact make up many of the most well-known and prominent stars int he night sky, such as [[Castor]].  Three of the six closest known stars are visual binaries: [[Alpha Centauri]], [[Luyten 726-8]], and [[Sirius]].

Visual binaries are quite common and in fact make up many of the most well-known and prominent stars in the night sky, such as [[Castor]].  Three of the six closest known stars are visual binaries: [[Alpha Centauri]], [[Luyten 726-8]], and [[Sirius]].

===Spectroscopic Binaries===

===Spectroscopic Binaries===

===Optical Binaries===

===Optical Binaries===

An optical binary are two stars that visually appear next to each other from the point of the observer using the unaided eye.  The reason for this is the two stars are usually along the line of sight of the observer, giving the illusion they are part of a binary pair.  However in reality the two stars are actually a great distance from each other and are not gravitationally bound as a single system.  A prime example of this is [[Alpha Capricorni]], traditionally seen as a binary with the individual stars referred to as α¹ Capricorni and α² Capricorni, however the former is 690 light years away, while the latter is only 109 light years away from [[Earth]] respectively.

An optical binary are two stars that visually appear next to each other from the point of the observer using the unaided eye.  The reason for this is the two stars are usually along the line of sight of the observer, giving the illusion they are part of a binary pair.  However, in reality the two stars are actually a great distance from each other and are not gravitationally bound as a single system.  A prime example of this is [[Alpha Capricorni]], traditionally seen as a binary with the individual stars referred to as α¹ Capricorni and α² Capricorni, however the former is 690 light years away, while the latter is only 109 light years away from [[Earth]] respectively.

==Cataclysmic Binary==

==Cataclysmic Binary==