Messier 99 is a grand design spiral galaxy, completely unbarred and with two giant spiral arms. One of the spiral arms is normal and the other appears distorted. M99 is slightly asymmetric in shape. The nucleus is shifted from the galaxy’s center. This is likely due to interactions with other galaxies in the Virgo Cluster.
Check out the annotated version in Astrobin.
This galaxy seems to be known as both the Virgo Pinwheel Galaxy and St. Catherine’s Wheel. It is located in the northern constellation Coma Berenices, approximately 49,000,000 light-years from the Milky Way. That’s 49 million times 5.8 trillion miles away.
I imaged this over two nights from my driveway in January 2025. I used an RC8 with an ASI071MC camera atop a Skywatcher Eq6r Pro mount. It consists of 128 180″ exposures calibrated, integrated and processed manually using PixInsight.
