Saturday, Jul 20, 2024

Located at a distance of about 23 million light years from Earth, the Vortex Galaxy or Whirlpool Galaxy is one of the brightest galaxies in the sky, by virtue not only of its apparent size (the angular diameter is about 11.2 minutes of arc), but above all of the very brilliant clusters of young blue stars, scattered along the entire path of its spiral arms. Also known as Messier 51 (M51) or NGC 5194, it was discovered by Charles Messier on 13 October 1773. That beige spot, partially covered by the long spiral arm of M51 (with which it interacts) is another galaxy. It is called NGC 5195 (or M51b), smaller and less luminous. It was identified only eight years later, in 1781, by Pierre Méchain. The spiral structure of M51 was instead observed for the first time much later, in 1845, by Lord Rosse (William Parsons, 3rd Earl of Rosse), who drew an unmistakable sketch of it. Filmed on February 16th and 17th for 9 hours in relay with M1, already published, I used Optolong L-Pro and RGB filters for luminance and color, while for hydrogen an HA filter, all processed in HALRGB.