IC 1318 is a vast field of glowing hydrogen gas in Cygnus, wrapped around the bright star Sadr (Gamma Cygni) — though the two aren’t actually related. Sadr sits a mere 1,800 light-years away, while the nebula itself lies roughly three times farther out at around 4,900 light-years; the star only appears embedded in the nebulosity because it happens to lie along the same line of sight from Earth. The gas isn’t even lit by Sadr — the true ionising source is a hot O9-class star buried deeper in the dust, invisible to the eye but energetic enough to excite the surrounding hydrogen across hundreds of light-years. The result is one of the largest and faintest emission nebula complexes visible from Earth, its wing-like lobes either side of Sadr giving it the popular nickname the Butterfly Nebula.