RS Puppis: Hubble has captured Light Echo

By watching the variable star RS Puppis, Hubble has captured a beautiful, and useful, phenomenon known as a light echo.
When most of the hydrogen is consumed, some stars evolve into very different states known as variable stars.
They become unstable and start pulsating.
Expanding and shrinking over several days or weeks and growing brighter and dimmer.
RS Puppis is one such variable star.
Hubble gazed at RS Puppis over around 5 weeks back in 2010 and observed it growing brighter and dimmer within its murky surroundings.
It appears that the gas around the star is expanding outwards.
However, this gas is not actually moving - it is an optical illusion known as a light echo.
The dusty environment around RS Puppis allows us to see this light echo with stunning clarity.
As the star expands and brightens, some of the light does not reach Hubble directly but is first reflected off progressively more distant shells of dust and gas surrounding the star.
This reflected light has further to travel, and so arrives at the Earth later than the light that has traveled straight from star to telescope.
Hubble also observed a light echo around the variable star V838 Monocerotis in 2002.
This is very much like the experience of an audible echo where the listener hears a sound once and then again as the second wave takes a longer path bouncing off surrounding objects.
Beyond the striking beauty of this effect, there is an important scientific reason to observe Cepheids like RS Puppis.
The period of their pulsations is known to be directly connected to their intrinsic brightness, which allows astronomers to use them as cosmic distance markers.
Astronomers have measured the distance to RS Puppis, calculating it to be around 6500 light-years, the most accurate distance to such a star ever measured.
Credits:
HubbleESA
• Hubblecast 71: Visible... By

[@winston1788]

Just a bit above my pay grade.😮