Messier 95, also known as NGC 3351, is a barred spiral galaxy about 33 million light-years away in the constellation Leo. M95 is one of several galaxies within the M96 Group, the other Messier objects of which are M96 and M105.
The galaxy has a morphological classification of SB(r)b, with the SBb notation indicating it is a barred spiral with arms that are intermediate on the scale from tightly to loosely wound, and an “(r)” meaning an inner ring surrounds the bar. The latter is a ring-shaped, circumnuclear star-forming region with a diameter of approximately 70,000 light-years. The spiral structure extends outward from the ring.
Its ring structure is about 3.5×108 M☉ (solar masses) in molecular gas and yields a star formation rate of 0.38 M☉ yr−1. The star formation is occurring in at least five regions with diameters between 100 and 150 pc that are composed of several star clusters ranging in size from 1.7 to 4.9 pc. These individual clusters contain (1.8–8.7)×106 M☉ of stars, and may be on the path to forming globular clusters.
A Type II supernova, designated as SN 2012aw, was discovered in M95 in 2012. The light curve of this displayed great flattening after 27 days, thus classifying it as a Type II-P, or “plateau”, core-collapse supernova. The disappearance of the progenitor star was later confirmed from near-infrared imaging of the region. The brightness from the presumed red supergiant progenitor allowed its mass to be estimated as 12.5±1.5 M☉.
