Messier 95 (also known as NGC 3351) is a barred spiral galaxy of about 75,000 light-years across, located some 38 million light-years away in the constellation of Leo, which is receding from us at a speed of some 778 kilometers per second. It is a member of the Leo I or M96 group, a group of galaxies in the constellation Leo which also contains M96, M105 and a number of fainter galaxies.
Messier 95, which contains billions of stars, has a pronounced spiral structure with nearly circular arms before they spread out. The arms are traced by dark dust lanes, young open clusters of bright blue stars, and telltale pinkish star forming regions.
Another striking feature of Messier 95 is a glowing yellowish core surrounded by a bright star-forming ring, with a diameter of almost 2000 light-years, where a large proportion of the galaxy’s star formation takes place. Its brightness is likely due to bursts of star formation.
On 16 March 2012 a Type II supernova, designated as SN 2012aw, was discovered in Messier 95. In this image it can be seen as the very bright star in a spiral arm on the sout-east.
A Type II supernova results from the rapid collapse and violent explosion of a massive star. A star must have at least 8 times, and no more than 40–50 times the mass of the Sun for this type of explosion. It is distinguished from other types of supernova by the presence of hydrogen in its spectrum. Type II supernovae are mainly observed in the spiral arms of galaxies and in H II regions, but not in elliptical galaxies.
Image Credit & Copyright: Adam Block, Mt. Lemmon SkyCenter, University of Arizona