Americanastrophysicist. In 1927 he explained the origin of strong green lines in the spectra of planetary nebulae. They are forbidden lines produced by a process now called Bowen fluorescence—in this case, transitions between atomic states in doubly ionized oxygen (O III) and not, as W. Huggins had earlier speculated, by an unknown element termed ‘nebulium’. This led to the correct identification of lines in the solar spectrum that had been similarly attributed to a hypothetical ‘coronium’, and thence to advances in the spectroscopic study of the compositions, temperatures, and densities of the Sun, stars, and nebulae.
Subjects: Astronomy and Astrophysics.