born in Syria. He was the first to detect systematic differences in the spectra of giant and dwarf stars. From 1914, with the German astronomer Arnold Kohlschütter (1883–1969), Adams developed methods of establishing the surface temperature, luminosity, and distance of stars from their spectra. In 1918 he showed that the density of the white dwarf Sirius B is 50 000 g/cm³. Adams also carried out spectrographic studies of the atmospheres of Mars and Venus.