Astronomy Bio...Carl Seyfert

Jay Bitterman

Carl Keenan Seyfert was an American astronomer and astrophysicist whose interests in photometry, the spectra of stars and galaxies, and the structure of the Milky Way resulted in the identification and study of the type of galaxy that now bears his name.

Seyfert was born on February 11, 1911 in Cleveland, Ohio. In 1933 he graduated from Harvard with a BSc. In 1935 he received his MA and his PhD in 1936 in astronomy while he was Parker Fellow at Harvard. He then worked at the McDonald Observatory in Chicago for four years, carrying out research on the spectra of stars in the Milky Way. In1940 He joined the Mount Wilson Observatory as National Research Fellow. From 1946 to 1951 he was Director of Barnard Observatory. Subsequently he was appointed Professor of Astronomy at Vanderbilt University, where he eventually became Director of the Arthur S. Dyer Observatory.

In 1943 he studied a series of 12 active spiral galaxies which have barely perceivable arms and exceptionally bright nuclei. His investigations revealed that these galaxies consist of small, exceptionally bright nuclei, often bluish in color, and have distinctive spectral lines indicating the emission of radio waves and infra-red energy. The highly excited spectra of these galaxies indicated that they contained hydrogen in addition to ionized oxygen, nitrogen and neon. Sulfur, iron and argon were also common to such galaxies. On the basis of their spectra, Seyfert divided the galaxies into two types, I and II.

Radiation from the nuclei of the galaxies is due to the very hot gases contained in their centers. The gases are subject to explosions which cause them to move violently. They obtain speeds of many thousands of kilometers per second relative to the center of the galaxy in the case of Type I, and of several hundreds of kilometers per second in the case of Type II galaxies. Seyfert galaxies also emit quite a large quantity of X-Rays and differ from other active galaxies in that they exhibit substantial amounts of non thermal emission.

There are only a small percentage of galaxies that exhibit these and related phenomena. Seyfert's original list has been expanded and these galaxies are still the subjects of research. The most intensively studied are NGC 1068, 1275 and 4151. Their spectra are so rich, however, that it is not possible to construct any single model that will satisfactorily account for all the known characteristics.

In 1951 Seyfert commenced to study objects now known as Seyfert's Sextet, a group of diverse extra galactic objects. Five are spiral nebulae and one an irregular cloud. One member of the group is moving away from the others at a velocity nearly five times that at which the others are receding from each other. Seyfert's original proposal, however, that the six were grouped together because of a chance meeting between objects at different distances is not now the accepted explanation.

Besides his research works in astronomy, Seyfert had a number of administrative posts, which included a civilian membership in the National Defense Research Committee. He was also a member of the International Astronomical Union and the American Astronomical Society and a Fellow of the Royal Astronomical Society. He died in 1960.