This is a sequence of images of the supergiant star V838 Monocerotis that had a stellar outburst (or nova in January 2002. The light bounces off the surrounding layers of dust as it travels through space. The light that travels to us on a direct path arrives first and the reflected light further way from the star reaches us later. It's like turning on a giant light bulb in the middle of space for a certain period of time in order to reveal information about the structure of these shells. This phenomenon is called a light echo.