Changes

Binary pairs have been observed in protostars that have yet to reach the main sequence, suggesting that binaries form in the early stages of star formation.  This could be due to the fragmentation of the molecular cloud as the stars first form, allowing for multiple stars to be created in the same system.<ref>http://www.phys.lsu.edu/astro/nap98/bf.final.html</ref>

Binary pairs have been observed in protostars that have yet to reach the main sequence, suggesting that binaries form in the early stages of star formation.  This could be due to the fragmentation of the molecular cloud as the stars first form, allowing for multiple stars to be created in the same system.<ref>http://www.phys.lsu.edu/astro/nap98/bf.final.html</ref>

Because most binary stars are of different masses, one will evolve off the main sequence before its companion.  In this scenario, several different events may happen.  The two stars may remain '''detached''' if the companion is far enough away in distance, and not very gravitationally massive.  The two stars will be ''semi-detached'' if the star that has evolved into the giant star is gravitationally close enough to its companion and exceeds its [[Roche lobe]], accruing mass from its companion. In this situation, much of the giant's mass will transfer to the companion star, actually making it the more massive of the two, despite still being in the main sequence.  [[Algol]] is the prime example of this.  

Because most binary stars are of different masses, one will evolve off the main sequence before its companion.  In this scenario, several different events may happen.  The two stars may remain '''detached''' if the companion is far enough away in distance, and not very gravitationally massive.  The two stars will be ''semi-detached'' if the star that has evolved into the giant star is gravitationally close enough to its companion and exceeds its [[Roche lobe]], losing mass to its companion through accretion. In this situation, much of the giant's mass may transfer to the companion star, actually making it the more massive of the two, despite still being in the main sequence.  [[Algol]] is the prime example of this.  

In some situations, the two stars of the binary system are so close that the expanding giant may actually come in atmospheric contact with its companion.  This is known as a '''contact binary'''. In this situation, the very close companion may cause the atmosphere of the giant to literally "splash away," leaving a naked core.  The companion, meanwhile, may spiral towards the core of the once giant from the friction of their atmospheres.  The result will be a merged core that becomes a white dwarf.<ref name="psu">http://www.astro.psu.edu/users/rbc/a1/lec16n.html</ref>

In some situations, the two stars of the binary system are so close that the expanding giant may actually come in atmospheric contact with its companion.  This is known as a '''contact binary'''. In this situation, the very close companion may cause the atmosphere of the giant to literally "splash away," leaving a naked core.  The companion, meanwhile, may spiral towards the core of the once giant from the friction of their atmospheres.  The result will be a merged core that becomes a white dwarf.<ref name="psu">http://www.astro.psu.edu/users/rbc/a1/lec16n.html</ref>