symbol ultimately from Latin and used by scribes writing Old English for a vowel sound between "a" and "e;" generally replaced by -a- after the Conquest. The Latin symbol represented Greek -ai-, and when Latinate words flooded into English in the 16c., it reappeared with them, but only as an etymological device, and it was pronounced simply "e" and eventually reduced to that letter in writing (e.g. eon) in most cases except proper names: Cæsar, Æneas, Æsculapius, Æsop.
American astronomer who studied binary stars and developed methods to calculate their mass and distances. Working independently of Ejnar Hertzsprung, Russell also demonstrated the relationship between types of stars and their absolute magnitude. This correlation is now known as the Hertzsprung-Russell diagram.