The bright star RS Puppis at the center of this image is surrounded by a cocoon of reflective dust. The super star is ten times more massive than the Sun, 200 times larger, and averages over 15,000 times brighter than the Sun. Averages? Yes, it is one of the most luminous Cepheid variable stars, and its brightness varies rhythmically over a six-week period.
The surrounding nebula flickers in brightness as pulses of light from the Cepheid propagate outwards. By tracking the fluctuation of light in RS Puppis itself and recording the faint reflections of light pulses moving across the nebula, astronomers are able to measure these light echoes and compute the distance to the star with about one percent uncertainty. The distance to RS Puppis is just about 6,500 light-years.
Image Credit: NASA / ESA