Light echoes from an exploding star. Sequence of four Hubble Space Telescope images of dust shells around the star v838 Monocerotis. This star underwent a massive brightening in January 2002, temporarily becoming the brightest star in the galaxy. The light from this outburst reflects from a series of dust shells around the star, which are thought to have been ejected during previous activity. From top left, the images were taken on 20th May, 2nd September, 28th October and 17th December 2002. The phenomenon allows study of the fine structure of the dust shells, which could help explain why the star behaves as it does.