A sequence of pictures from Hubble's Advanced Camera for Surveys demonstrating the echoing of light through space caused by an unusual stellar outburst in January 2002. A burst of light from the star is spreading into space and reflecting off surrounding shells of dust to reveal a multicoloured 'bull's eye'. This sequence of pictures from May to December 2002 shows apparent changes in the circumstellar dust as different parts are illuminated sequentially in an effect called a 'light echo'. From the first to last image the diameter of the nebula appears to balloon from 4 to 7 light-years. This creates the illusion that the dust is expanding into space faster than the speed of light. In reality it is simply the light from the stellar flash that is sweeping out into the nebula

Photograph: Nasa/Esa