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Of tides and Seyfert galaxies.

Seyfert galaxies, like the one in this picture, often show curious shapes. Many of their features seem to be the result of tidal interactions with other galaxies. One of those, NGC 7674, shows here two tails that seem to be the result of extreme tidal interaction with some other galaxy.

Seyferts are galaxies with particularly active and energetic nuclei. Astrophysicists believe them to be intermediate between "normal" galazies, which have less activity in their nuclei, and quasars, which are considered the most energetic of active galactic nuclei. Astronomers have thought that Seyfert galaxies show evidence of tidal interaction more often than less active galaxies. The survey that produced this picture was done by John W. MacKenty of the University of Hawaii. It shows that 25 to 30 percent of Seyferts have such peculiar shapes. This result supports the opinion that they are involved in tidal interactions more often than are other galaxies. Astrophysicists believe that the source of the energy emitted by galactic nuclei is an engine powered by a black hole. Such tidal interactions may be a way of obtaining a continuous supply of gaseous fuel for the black hole.

MacKenty observed with the University of Hawaii's 88-inch telescope on Mauna Kea and presented his report in Charlottesville, Va., at the recent meeting of the American Astronomical Society.
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Title Annotation:tidal interaction between galaxies
Author:Thomsen, Dietrick E.
Publication:Science News
Date:Jul 6, 1985
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