Photograph
Western Veil Nebula
An astrophotograph of the Western Veil, where delicate filaments of glowing gas trace an ancient supernova remnant.
Beyond the frame
The delicate filaments are not the entire supernova remnant. They trace the places where the expanding shock wave passes through interstellar gas and heats it until it begins to glow. In effect, we are seeing only the edge of an enormous bubble more than 100 light-years across—a moment in the continuing journey of a shock wave through our galaxy.