24 July
1853: On 24 July 1853, Henri-Alexandre Deslandres was born.
Deslandres was a French astrophysicist who invented a spectroheliograph to photograph the Sun in monochromatic light and made extensive studies of the solar chromosphere and solar activity.
His investigation of molecular spectra produced empirical laws anticipating those of quantum mechanics. He observed spectra of planets and stars and measured their radial velocities, and he determined the rotation rates of Uranus, Jupiter and Saturn.
