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Scientists improve our understanding of the way that stars evolve

Scientists have found a pulsating ancient star, in a double star system, that will help improve our understanding of the way that stars like the sun evolve and die.

The discovery of the first pulsating white dwarf star, in an eclipsing binary, means we can see how binary evolution has affected the internal structure of a white dwarf in detail for the first time.

An eclipsing binary, or double star system, is made up of two stars orbiting each other and periodically passing in front of each other as seen from the Earth. Binary evolution occurs when the stars in a double star system are close enough to transfer their mass to each other. This subsequently changes both of the stars’ structure and their evolution.

The scientists at the University of Sheffield, including STFC Ernest Rutherford fellow, Dr Steven G. Parsons, discovered the star using HiPERCAM, a revolutionary high-speed camera. The HiPERCAM instrument can take one picture every millisecond simultaneously in five different colours. This allowed the researchers to detect rapid and subtle pulsations from this particular white dwarf.

The pulsations of the white dwarf star and the eclipsing binary system allowed the team to investigate the structure of it using two techniques, asteroseismology and eclipse studies. Asteroseismology involves measuring how fast sound waves travel through the white dwarf. Eclipse studies measure the shape of the eclipse (i.e. how long does the eclipse last, how deep is it) to determine the sizes of the two stars.

The lead on the project, Dr Steven G. Parsons yesterday stated:

“The pulsating white dwarf that we discovered, is extremely important because we can use the binary motion and the eclipse to independently measure the mass and radius. This helps us to determine what the white dwarf is made of.

“Even more interestingly, the two stars in this binary system have interacted with each other in the past, transferring material back and forth between them. We can see how this binary evolution has affected the internal structure of the white dwarf, something that we've not been able to do before for these kinds of binary systems.”

The next step of the research, which has been published in Nature Astronomy, is to continue observing the white dwarf to record as many pulsations as possible using HiPERCAM and the Hubble Space Telescope. 


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