Hermann Carl Vogel

Hermann Carl Vogel (born 3 April 1841, died 13 August 1907) was a German astronomer. He was born in Leipzig, Kingdom of Saxony.
Vogel was one of the first astronomers to use a spectroscope in astronomy. He used it to read the chemicals on planets far away and to measure the time it takes the Sun to spin. He could read it by measuring the Doppler effect.
In 1882, Vogel became the Director at the Astrophysical Observatory Potsdam and he is best known for some work there in 1890. Vogel found that the colour of some stars changed over time, becoming red and then later becoming blue. His idea was that the star was moving toward and then away from the Earth, and that the colour changes were the because of that movement. These stars seemed to be orbiting around a hidden star as if they were double-stars but the second star could never be seen, only known by the colour changing Doppler effect.
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.
Medals of Hermann Carl Vogel.
Awarded to Hermann Carl Vogel