Cigar galaxy (M82). This galaxy has been distorted by its gravitational interaction with the more massive galaxy M81 (out of frame at top), which passed close to it several million years ago. This interaction triggered a massive increase in starbirth in M82. This is responsible for its pink colour, as pink light is emitted as hydrogen gas is ionised by the radiation from the hot newborn stars. Starbirth in M82 occurs at a rate around ten times that of normal galaxies. M82 lies just 150,000 light years from M81, and the pair are some 12 million light years from Earth in the constellation Ursa Major.