M81 is a large spiral galaxy in Ursa Major that is reasonably local to us at 12 million light years. Its companion, M82 has been disrupted by an encounter with M81 in the past.
M82 is a starburst galaxy with intense star formation triggered by the gravitational influence of M81. The red fan-like filaments at right angles to the axis of the galaxy are formed by a “superwind”. The intense star formation has resulted in multiple supernovae explosions occurring about once every 10 years – the explosions power the super wind. The filaments are expanding outwards at about 600 miles a second and glow brightly in hydrogen alpha (red). They are also a very strong source of radio emission, listed as 3C 231 in the 3rd Cambridge catalogue of radio sources.
I tried imaging the last supernova in M82- SN 2014J (Class 1a) in 2014 when I was just starting astrophotography. I think I just used a single 30 second exposure on a 300mm lens – not convinced I caught anything!
M82 is listed by itself in the Arp catalogue of peculiar galaxies as Arp 337. The pair (M81 and M82) are also listed in the paired galaxies section of the Arp catalogue.
A very, very faint patch of blue between 3 triangular stars under M81 is Holmberg IX – a small irregular dwarf galaxy under the gravitational influence of M81 – a bit like our Magellanic Clouds.
Sky and Telescope Magazine have some bonus digital content attached to their May 2016 edition that goes deep into M81 and M82 listing zones containing HII zones, SNR and radio/X-ray sources. I can just about pick out some of the main zones they mention at 200% magnification in Photoshop.
M82 contains a faint arrowhead pointing to the superwinds. This is composed of 4 brownish dots – regions A,C,D and E that each contain many Radio and X-ray sources, Massive star clusters and SNRs – these are some of the regions producing the superwinds from frequent massive SN explosions.
Its easier to pick out the listed regions in M81 and I can locate A through to G. A to D are bright HII regions. Eand F are listed as containing star cluster/globular cluster – somewhat humbling to be able to detect star clusters or globular clusters around a distant galaxy from a small backyard scope.