With the discussion of light echoes today, here’s another interesting one. In 2002 the star v838 Monocerotis swiftly brightened to about a million times the brightness of the Sun before dimming down again. This burst of light then traveled outward from the star, illuminating the gas and dust surrounding the star. Because the light burst was relatively short, this meant that successive layers of the gas and dust were illuminated as the sphere of light expanded.
In the image below, a collection of images taken between May 2002 and October 2004 have been put together. It should be emphasized that the gas and dust are not expanding outward, but the burst of light is expanding. Sometimes light echoes can be quite impressive.