M101 is a spiral galaxy, face-on to us. It was discovered by Pierre Mèchain in 1781. He informed Charles Messier, who included it in his catalogue. It’s a large galaxy with about 10 times the number of stars as our own, and it also has a larger diameter: about 170,000 light-years compared to the 100,000 light years for our Milky-Way Galaxy. It is 21 million light-years away.

M101 has a notably asymmetrical appearance, which is the result of tidal forces with a number of nearby companion galaxies. It also has a large number of bright star-forming regions, showing up red from the light of hydrogen ionised by the bright and hot, young stars.