M99 in Coma Berenices, at 50 to 60 million light years away, is part of the Coma-Virgo galaxy cluster, together with M88, M91, M98, M100 and several other galaxies.

It is an inclined galaxy known for its strong one-armed structure. The south arm is filled with bright star-forming regions while the north arm is weak. This dichotomy is unexplained by optical observations, but radio images show clouds of neutrl hydrogen perturbing the the spiral from the south. The one armed appearance is evident in a 12" or large telescope, which shows a bright core 1" across with the prominent arm wraping from the east edge to the south. This spiral arm is mottled and ends at a stellar association. The northern arm is barely visible in a 12" aperture and does not wrap as tightly around the core.

M99 Observer´s Log