Original: By obtaining periodic Doppler shifts in the components of Algol , Vogel proved that the latter was a binary star ; thus , Algol was one of the first known spectroscopic binaries ( and it is also known to be an eclipsing binary ) .
Simplified: Volgel proved that Algol was a double star that could not be seen ( spectroscopic binary star ) and it was one of the first of these double stars proven to exist .