"Light-Echo" from an Exploding Star

A Light echo is a visual phenomenon seen when light from a rapidly brightening object such as a nova is reflected from interstellar matter. Imagine a camera-flash in space - it's an expanding sphere of light. Likewise from NASA, we have a star which has exploded. What you're seeing in these images is the light-burst traveling outwards in all directions as it illuminates dust and gas previously blown-off by the star. For a size comparison, our entire Solar System would fit easily inside the red aura around the star, look again at the dates on the images and remember that light travels at roughly 186,000 miles per second and these pics span 6 months. Amazing.