Hubble Images the Light Echo in RS Puppis

This movie shows the reflection nebula around the Cepheid variable RS Puppis at seven equally spaced intervals during its 41.4-day pulsation period. Each time RS Puppis reaches maximum brightness, it sends another wave of illumination into the surrounding dust. Thus a pattern of apparently expanding bull's-eyes surrounds the variable star, similar to the ripples in a pond produced when a series of stones is thrown into the water. These images were taken with Hubble's Advanced Camera for Surveys in a visual filter over the following dates in 2010: March 25 and 31, April 6, 11, 18, 24, and 29. Each individual image in this sequence had an exposure time of 23 minutes.