The Whirlpool galaxy was discovered by Charles MESSIER in 1773 in the constellation of Canes Venatici. it is over 30 million light-years away.
This surprising galaxy is the result of the encounter of two galaxies, a large one with a spiral structure, and a small one that can be seen at the end of one of the "arms" of the spiral.
MESSIER 51 can be observed through a telescope of at least 10 cm in diameter as a blurred spot, but the spiral structure can only be seen using a 25 cm diameter telescope.
"Chamois" (the person's pseudonym on the Futura-Sciences astro forum) produced this fine image using a digital camera and a 200 mm diameter telescope; an exposure time of 2 hours 45 minutes was necessary to reveal the rich structure of the galaxy's spiral arms.
Whirlpool galaxy - 1 Photo