The beautiful face-on galaxy, M101 was discovered in 1781.
It is estimated to have a mass of equivalent to about 16 
billion of our suns or only 10% of the Milky Way. This 
makes it one of the lowest density galaxies known. M101 
is also believed to be about 90,000 light years in diameter.

A total of 3 supernovae have been observed in M101,
in the years 1903, 1951 and 1970.