The Pinwheel Galaxy – Messier 101
M101 is a large face-on spiral galaxy located 22 million light-years away in the constellation of Ursa Major. At magnitude +7.9, it can be glimpsed in binoculars or small telescopes from dark sites but suffers from low surface brightness and in bad seeing conditions or light polluted areas, the galaxy can be difficult to spot. It’s best seen from the Northern Hemisphere during the months of March, April and May.
M101 is also known as “The Pinwheel Galaxy” and was discovered by Pierre Méchain on March 27, 1781. He described it as “nebula without star, very obscure and pretty large, 6′ to 7′ in diameter, between the left hand of Bootes and the tail of the great Bear.” He communicated this to Charles Messier who verified its position and then included it in his catalogue as one of the final entries.
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)