Messier 81 (LRGB)


M81 is a relatively close spiral galaxy at “only” 12 million light years away. It is a grand design spiral galaxy. It has a diameter of 90,000 light years. It still astounds me that amateur equipment can see nebulae in a galaxy that far away.

M81 is in the constellation Ursa Major (home of the Big Dipper). It’s also known as Bode’s Nebula (or sometimes Bode’s Galaxy) named after Johann Bode who first discovered it in 1774. Bode called it a nebula because astronomers back then didn’t know that these were galaxies (something not confirmed until the early 20th century).

I’ve included a second image processed from the same data. This one is pushed a bit farther to show the integrated flux nebula. This is dust outside the main body of our galaxy that is reflecting the light of the whole galaxy back at us. It is very, very faint and I was not able to do a particularly good job making a pleasing image from it which is why the image above is the headliner.

The IFN is primarily visible in the bottom right running up the frame and then arching over the top of M81. There is also an irregular dwarf galaxy, PGC 28757, below M81 that is just visible in the first image. It’s a companion to M81 much like the Magellanic Cloud irregular galaxies are to our own Milky Way.

For all the processing technical details, see astrobin.

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