- M 81 and M 82
M 81 and M 82 are a pair of galaxies located in the Northern sky in the constellation Ursa Major. In my image, M 81 (NGC 3031) is the large spiral on the right, while M 82 (NGC 3034) is the irregular galaxy on the left. The pair lie at a distance of around 11.6 million LY, separated by only around 125,000 LY. M 82 is gravitationally bound to M 81, and since M 81 is around 10 times more massive than M 82, M 82 has suffered more as a result of this relationship. Previous encounters with M 81 have distorted the shape of M 82 and led to intense star formation in it (M 82 is considered the "classic" example of a Starburst Galaxy). The elongated shape of M 82 has led to some calling it the "Cigar Galaxy". The most recent encounter between the two galaxies occurred around 10 million years ago, wherein the whole structure of M 82 was disrupted. The red glow around the center of M 82 (which shows up even better in longer exposures) represents a "superwind" of hot gasses being driven out of the galaxy by intense star formation at speeds approaching 800 km/sec. M 82 is also a strong radio source. M 81 has been largely unaffected by these encounters, although the lower spiral arm exhibits a slight bend in the direction of M 82.
M 81 and M 82 were both discovered on the night of 31 December 1780 by the German astronomer Johann Elert Bode, Messier's rival in astronomical discoveries. Messier observed the pair two months later.
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