Object Analysis

Messier 99 (M99), also known as the "Coma Pinwheel," is an unbarred spiral galaxy in the constellation Coma Berenices. It is a grand design spiral, famous for its well-defined and symmetrical arms. M99 is located about 50 million light-years away in the Virgo Cluster and is one of the most photogenic galaxies in the northern sky.

The galaxy is unusual because its spiral arms are asymmetrical; one arm is much more extended and "drawn out" than the others. This distortion is likely caused by a past gravitational encounter with a nearby neighbor, possibly the dark galaxy VIRGOHI21. This interaction acted like a cosmic tug, pulling on the gas and stars of one arm.

M99 has a very high rate of star formation—nearly three times higher than other galaxies of its size. This "starburst" activity is evident in the hundreds of bright pink nebulae and blue star clusters that dot its arms. It has also been the site of four observed supernovae in the last century, making it an incredibly active and evolving system.