Light echoes whisper the distance to a star

The nebula around the Cepheid star RS Pup undoubtedly holds a wealth of information about the mass-loss history of this star. It will thus be instrumental to understand the evolution of Cepheids. Less than five years away from the centenary of the discovery of the Period-Luminosity relation by Leavitt & Pickering, RS Pup could well become a 'Rosetta stone' for this important class of stars. This colour composite image is based on observations made with the 3.6-m ESO New Technology Telescope (NTT) installed at the La Silla Observatory (Chile) and equipped with the ESO Multi-Mode Instrument (EMMI). The image is based on data obtained through B, V, and R-filters. In order to avoid a heavy saturation of the detector, RS Pup was positioned in the gap between the detectors.