M81, M82 & NGC3077

M81 (Bode’s Galaxy) and M82 (Cigar Galaxy) are prominent members of the M81 galaxy group in the constellation Ursa Major, at a distance of about 12 million light years. M81 is a large, almost symmetric spiral galaxy with pronounced spiral arms and a central bulge. M82, by contrast, appears as an irregular galaxy disturbed by gravitational interactions, with pronounced dust bands and a high star-formation rate in its central region.

East of M81 lies NGC 3077, an irregular dwarf galaxy at a similar distance, which is also clearly affected by interactions within the group. The gravitational effects have created extended structures of neutral hydrogen (HI) as well as filaments of intergalactic gas running between the galaxies. These structures can only be detected through sensitive radio observations or special image-processing techniques in the optical spectrum.

In the foreground of the image there is also extensive galactic cirrus — streaky structures of interstellar dust within the Milky Way that scatter sunlight or integrated starlight. These highly diffuse nebulae are photometrically extremely faint and pose a challenge when processing and interpreting extragalactic fields.