Astronomers using NASA’s Hubble Space Telescope have observed RS Puppis – a type of star known as a Cepheid variable star – over a period of five weeks.
This image shows the variable star RS Puppis. Image credit: NASA / ESA / the Hubble Heritage Team / STScI / AURA / Hubble-Europe Collaboration / H. Bond, STScI and Penn State University.
RS Puppis lies in the constellation of Puppis about 6,500 light-years away from Earth. This star is over 10 times more massive and 200 times larger than our Sun, and 15,000 times more luminous. It rhythmically brightens and dims over a 6-week cycle.
RS Puppis is unusual. It is shrouded by thick, dark clouds of dust enabling a phenomenon known as a light echo to be shown with stunning clarity.
Hubble observed the star and its environment over a period of five weeks in 2010, capturing snapshots at different stages in its cycle and enabling astronomers to create a time-lapse video.
As RS Puppis expands and brightens, astronomers see some of the light after it is reflected from progressively more distant shells of dust and gas surrounding the star, creating the illusion of gas moving outwards.
This reflected light has further to travel, and so arrives at the Earth after light that travels straight from star to telescope. This is analogous to sound bouncing off surrounding objects, causing the listener to hear an audible echo.
While the light echo effect is certainly striking in itself, there is another important scientific reason to observe Cepheids like RS Puppis.
The period of their pulsations is known to be directly connected to their intrinsic brightness, a property that allows astronomers to use them as cosmic distance markers.
A few years ago, astronomers used the light echo around RS Puppis to measure its distance from us, obtaining the most accurate measurement of a Cepheid’s distance.
Studying stars like RS Puppis helps scientists to measure and understand the vast scale of the Universe.
