Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
Acknowledgment: H. Bond (STScI and Penn State University)
Acknowledgment: H. Bond (STScI and Penn State University)
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.
What I find so interesting about this picture is that it reveals subtle color changes in the light echoes of RS Puppis. Cepheids do change color slightly during their light cycle, becoming slightly bluer as they suddenly release heat that has been built up in their cores. In this figure, the way the cepheid star changes color and size during its light cycle can be seen in the color and size of the filled circles. These subtle Cepheid color changes show up in the light echoes of RS Puppis.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).
A final note: I would have posted this image in the Latest Sky Photography folder, but I couldn't find a "New topic" button there.
Ann
