Hermann Carl Vogel

His siblings included Eduard Vogel (1829–1856), Africa explorer and astronomer; Elise Polko (1823–1899), poet and singer and Julie Dohmke (1827–1913), writer, publisher, translator.

In Leipzig he was assistant to Karl Christian Bruhns and took part in measurements of double stars carried out by Friedrich Wilhelm Rudolf Engelmann.

Vogel was awarded a doctorate in 1870 from Jena for work on nebulae and star clusters and went in the same year to the Sternwarte Bothkamp of Kammerherrn von Bülow, c. 20 km south of Kiel.

He applied this instrument to chemically analyze planetary atmospheres and in 1871 he was the first to establish Sun's rotational period using the Doppler effect.

However, in each case the companion star could not be resolved using a telescope, and so these double-star systems were designated spectroscopic binaries.

[1] Vogel's technique was adopted by the Swiss astronomers Michel Mayor and Didier Queloz who announced the discovery of an exoplanet orbiting 51 Pegasi.