https://www.mnastro.org/mas-happenings-may-27-2025/ (fb)

With thanks to Suresh Sreenivasan for images and text. M100 (NGC 4321) is a Grand Design spiral galaxy, a galaxy with very prominent and well-defined spiral arms. Some grand designs we see face-on, like this one, giving us a complete view of the spiral arms and the internal structure. These are among the prettiest galaxies that we can see thru our telescopes. This galaxy was discovered by Pierre Mechain in 1781. It shines fairly brightly at magnitude +9.3, and is located about 55 million light years away in the constellation Coma Berenices. Astronomers believe that M100 is a very close approximation for what our own Milky Way galaxy might look like out in space, with its intricate spiral structure. It is around 107,000 light years across and contains around 400 billion stars, making it virtually the same size and mass as our Milky Way galaxy. M100 was one of the first spiral galaxies discovered, and is one of the brightest members of the Virgo galaxy cluster. It was included as one of the original 14 known “spiral nebulae” by the Earl of Ross of Ireland in 1850, who was using his 72” speculum reflector. Dubbed “Leviathan”, this was the largest telescope in the world at the time. He was the first to take note of the spiral structure. The intricate spiral structure of this galaxy can start to be picked up visually thru telescopes as small as 4” of aperture. On images, the complete internal structure is seen, including some pockets of blue in the spiral arms, indicating concentrations of young, very hot bluish stars. These stars are very massive and they live short lives, measured in the millions of years. When they run out of their nuclear fuel they explode as Type II supernovas. Indeed, five supernova have been observed in M100 over the past 125 years (1901B, 1914A, 1959E, 1979C and 2006X). This high level of new star production classifies M100 as a starburst galaxy. M100 is known for having an active galactic nucleus, powered by an energetic supermassive black hole that may contain 100 million times the mass of our Sun. As matter falls inwards towards the black hole, it radiates brightly, causing the galaxy’s core to brighten dramatically, as shown in these images. The bright elongated galaxy to the left of M100 is the spiral NGC 4312. It is listed as being magnitude +11.7, and it’s dimensions are 4.6’ x 1.1’. It is also around 55 million light years away, and is about 59,000 light years across. NGC 4312 is likely a companion galaxy of M100, as the two galaxies lie just 288,000 light years apart. NGC 4312 also displays a “crown” of reddish hydrogen, as shown in these images. It is likely that gravitational tugs from nearby M100 is stretching and heating this hydrogen, creating ripe conditions for new stars to be born. Data Captured: Friday April 25, 2025 Location: MAS Cherry Grove Observatory – Bortle 4 - Mallincam 10” f/8 Ritchey-Chrétien Telescope @ f/5.2 - ZWO ASIAir Plus / Baader 2” LRGB & 6.5nm H-alpha filter - ZWO ASI2600Pro for PS Cooled Monochrome CMOS Camera (set to -10C) - Celestron CGX-L Mount / Everything powered by AC 455 minutes (7.58 hrs) sLRGBHa (175/55/60/60/105) @ -10C Stacked, processed & cropped in PixInsight Post-processing in PhotoShop using the Starizona Action Pack (fb)