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.
NASA, ESA, G. Bacon (STScI), the Hubble Heritage Team (STScI/AURA)-Hubble/Europe Collaboration, and H. Bond (STScI and Pennsylvania State University)
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