Vogel, Hermann Carl (1842–1907)

German astronomer. He discovered spectroscopic binary stars. By measuring the Doppler effect in the spectral lines of stars to ascertain their velocity, he ended the controversy over the value of Christian Doppler's theory for investigating motion in the universe.

Vogel was born and educated in Leipzig and in 1863 began working at the observatory there. From 1882 he was director of the newly constructed Potsdam Observatory near Berlin.

Vogel worked intensively on the spectroscopic properties of planets, nebulae, the northern lights, comet III 1871, and the Sun, and examined the spectra of some 4,000 stars. He used spectrophotometry to study Nova Cygni 1876 and his results provided the first evidence that changes occur in the spectrum of a nova during its fading phase. He also used photographic spectra to catalogue stars, and introduced the photographic method for the accurate determination of their radial velocities.

Vogel's discovery of spectroscopic binary stars arose from a study of the periodic displacements of the spectral lines of the stars Algol and Spica, eclipsing binary stars whose components could not, at the time, be detected as separate entities by optical means. From his spectrographs, Vogel derived the dimensions of this double star system, the diameter of both components, the orbital velocity of Algol, the total mass of the system and in 1889, he derived the distance between the two component stars from each other.