Starship Asterisk*

http://heritage.stsci.edu/2013/51/caption.html wrote:

The bright southern hemisphere star RS Puppis is at the center of the image and is swaddled in a gossamer cocoon of reflective dust illuminated by the glittering star.

The superstar is ten times more massive than our Sun and 200 times larger. If viewed from any accompanying planets it would appear 15,000 times brighter than our Sun.

RS Puppis rhythmically brightens and dims over a six-week cycle. It is one of the most luminous in the class of so-called Cepheid variable stars.

The nebula flickers in brightness as pulses of light from the Cepheid propagate outwards. Hubble took a series of photos of light flashes rippling across the nebula in a phenomenon known as a light echo. Even though light travels through space fast enough to span the gap between the Earth and the Moon in a little over a second, the nebula is so large that light can actually be photographed traversing the nebula.

By observing the fluctuation in RS Puppis itself as well as recording the faint reflections of light pulses moving across the nebula, astronomers are able to measure these “light echoes” and pin down a very accurate distance. The distance to RS Puppis has been narrowed down to 6,500 light-years (with a margin of error of only one percent).