Seyfert galaxies are usually (but not always) spirals with very bright (almost starlike) nuclei, They exhibit a strong continuum from IR through X-ray regions of the spectrum, with emission lines that are sometimes variable (Here are spectra of Seyfert and other active galaxies - see the following description). The above image shows closeups of some Seyfert galaxies imaged by the Hubble Space Telescope. Here is an explanation of the images, and here is a link to more Seyfert images.


The adjacent right image shows a Hubble Space Telescope view of the Seyfert galaxy NGC7742, which is about 72 million light years away, in the constellation Pegasus (Ref). The central region is about 3000 light years across, and as for most Seyferts is very bright at visible wavelengths. It is likely that this region contains a huge black hole. Faint spiral arms surround the central region, and contain many blue star-forming regions.

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