the transient in archival Hubble images, indicating that the progenitor star was heavily obstructed by interstellar dust. 2019abn peaked at magnitude 17, reaching an intrinsic brightness of . Planet candidate In September 2020, the detection by the Chandra X-ray Observatory of a candidate exoplanet, named M51-ULS-1b, orbiting the high-mass X-ray binary M51-ULS-1 in this galaxy was announced. If confirmed, it would be the first known instance of an extragalactic planet, a planet outside the Milky Way Galaxy. The planet candidate was detected by eclipses of the X-ray source (XRS), which consists of a stellar remnant (either a neutron star or a black hole) and a massive star, likely a B-type supergiant. The planet would be slightly smaller than Saturn and orbit at a distance of some tens of astronomical units. Companion NGC 5195 (also known as Messier 51b or M51b) is a dwarf galaxy that is interacting with the Whirlpool Galaxy (also known as M51a or NGC 5194). Both galaxies are located approximately 31 million light-years away in the constellation Canes Venatici. Together, the two galaxies are one of the most widely studied interacting galaxy pairs. Galaxy group information The Whirlpool Galaxy is the brightest galaxy in the M51 Group, a small group of galaxies that also includes M63 (the Sunflower Galaxy), NGC 5023, and NGC 5229. This small group may actually be a subclump at the southeast end of a large, elongated group that includes the M101 Group and the NGC 5866 Group, although most group identification methods and catalogs identify the three groups as separate entities. Gallery See also List of Messier objects List of galaxies Messier object Messier 101 – another grand-design spiral galaxy New General Catalogue NGC 5195 – the companion galaxy to NGC 5194 References and footnotes External links SEDS: Spiral Galaxy M51 Whirlpool Galaxy at ESA/Hubble The Whirlpool Galaxy (Messier 51(a)/NGC 5194) M51 The Whirlpool Galaxy The Whirlpool Galaxy at Constellation Guide The Whirlpool Galaxy in the Staracle Messier catalog Unbarred spiral galaxies Interacting galaxies Peculiar galaxies M51 Group Canes Venatici Messier objects NGC objects 08493 47404 085 Seyfert galaxies 17731013 Discoveries by Charles Messier