Discovered in 1773 by Charles Messier, M 51 is a famous pair of interacting galaxies approximately 28 million light-years away from Earth in the direction of the constellation Canes Venatici.^[1] The larger M 51a was discovered in 1773 by Charles Messier, and its companion dwarf galaxy M 51b was discovered by his friend Pierre Méchain in 1781. The Whirlpool Galaxy is the first deep-sky object to be described as having a spiral structure, sketched by Lord Rosse in 1845. Debate over the nature of these “spiral nebulae” would later lead to the discovery that the Milky Way is just one of unthinkably many galaxies in the universe. The Whirlpool Galaxy is home to candidate exoplanet M51-ULS-1b, which would be the first known exoplanet outside our galaxy if confirmed. Initial observations suggest it is a Saturn-sized planet orbiting a binary system of a massive star and either a black hole or neutron star at a distance of about 10 astronomical units.^[2]

Captured using a Fujifilm X-A5 and a GSO 6" F/4 Newtonian mounted on a Celestron AVX, with a GSO Coma Corrector and guided with a ZWO ASI120MM Mini and an Svbony SV1665. This image is a stack of 55x90s exposures at 1250 ISO, calibrated with 30 flats, 21 darks, and 50 bias frames. Processed using (1) Siril for pre-processing, stacking, background extraction, and photometric color calibration, and (2) GIMP for wavelet decomposition, sharpening, and final color balance.