The cigar galaxy M82 got its striking, chaotic shape from a disastrous approach to a neighbouring galaxy ten times as massive (M81) several hundred million years ago. The strong gravity changed the structure of the cigar galaxy to such an extent that intense star formation processes and supernovae explosions were triggered. Matter is thrown out of the cigar galaxy, hydrogen gas falls back onto the galaxy and is ionised by the strong radiation of the young, hot stars. We see this process as glowing red hydrogen clouds protruding vertically from the galaxy.
Cigar Galaxy – M82