The Markarian galaxies are a class of galaxies that have nuclei with excessive amounts of ultraviolet emissions compared with other galaxies. Benjamin Markarian drew attention to these types of galaxies starting in 1963. The nuclei of the galaxies had a blue colour that in a star would be classed from A to F. This blue core did not match the rest of the galaxy. The spectrum in detail tends to show a continuum that Markarian concluded was produced non-thermally. Most of these have emission lines and are interesting because of their energetic activity. Markarian Catalogue entries are of the form "Markarian ####", and can frequently use the abbreviations Mrk, Mkr, Mkn; and rarely Ma, Mk, Mark.