The faint, filamentary arcs of SH2-91 trace the expanding remains of a massive star that exploded thousands of years ago in the constellation Cygnus. This supernova remnant is part of a larger, diffuse structure of glowing gas that stretches across the star-rich fields of the Milky Way. Delicate tendrils of hydrogen and oxygen emission form the faint ribbons that mark the shock fronts moving through interstellar space.

Although far less well-known than the nearby Veil Nebula, SH2-91 offers a glimpse of the same cosmic process: the recycling of stellar material into the galaxy. The remnants of the long-gone star continue to shape the interstellar medium, seeding it with heavier elements that will one day become part of new stars and planets.