and astrophysicist who studied the spectra of stars and galaxies, and
identified and classified the type of galaxy that now bears his name.
Seyfert was born in Cleveland, Ohio, and studied at Harvard. He was
director of Barnard Observatory 1946-51, and from 1951 professor at
Vanderbilt University and director of the observatory there. He was
a member of the National Defence Research Committee.
In 1943, Seyfert was studying 12 active spiral galaxies with bright
nuclei. His investigations showed that these galaxies contain hydrogen
as well as ionized oxygen, nitrogen, and neon. On the basis of their
spectra, Seyfert divided the galaxies into two types, I and II. Seyfert
galaxies emit radio waves, infrared energy, X-rays, and nonthermal radiation.
The gases at their centres are subject to explosions which cause them
to move violently, with speeds of many thousands of kilometres per second
relative to the centre of the galaxy in the case of type I, and of several
hundreds of kilometres per second in the case of type II.
In 1951, Seyfert began a study of the objects now known as Seyfert's
Sextet: a group of diverse extragalactic objects, of which 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.