M81, although appearing in Messier's catalogue, was not discovered by him, but by Johann Bode on New Year's Eve, 1774. He also discovered M82 at the same time. Like M82 it is about 12 million light-years away. Like most galaxies (including our own), it harbours a super-massive black hole at its centre, and in this case it is estimated to be the equivalent of 70 million times the mass of our sun, all compressed into a single, infinitesimally small point.