ABSTRACT
M51 Object 51 in the Messier list, a bright Sc spiral galaxy notable for the grand design of its spiral arms (and sometimes referred to as the “Whirlpool” galaxy). M 51 is perturbed by a smaller companion galaxy which appears to be in touch with and distorts one of its spiral arms. Optical spectra of the M 51 nucleus show emission lines suggestive of non-thermal nuclear activity, and whose intensity ratios are intermediate between those of LINERs and Seyfert 2 nuclei.
