Scientists Discover Pulsating Remains of a Star
A team of scientists at the University of Sheffield have discovered a pulsating ancient star in a double star system. This discovery will allow the team to gain important information on the history of how stars evolve and eventually die. The findings have been published in Nature Astronomy.
The discovery of the first ever pulsating white dwarf star in an eclipsing binary will help the researchers understand how binary evolution has affected the internal structure of a white dwarf in detail.
An eclipsing binary is made up of two stars orbiting each other and periodically passing in front of each other.
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Determining what a white dwarf is made of is not straightforward because these objects have about half of the mass of the Sun, packed into something about the size of the Earth. This means that gravity is extremely strong on a white dwarf, around one million times larger than here on Earth, so on the surface of a white dwarf an average person would weigh about 60,000,000kg. The gravity causes all of the heavy elements in the white dwarf to sink to the centre, leaving only the lightest elements at the surface and so the true composition of it remains hidden underneath.Dr. Steven Parsons, Department of Physics and Astronomy, University of Sheffield
When a star dies it leaves behind its burnt out core, thus creating a white dwarf. They are thought primarily to be made up of carbon and oxygen but this newly discovered white dwarf is made mostly of helium. The scientists believe that this composition is due to to its binary companion, cutting off its evolution early thus reducing its chance to fuse the helium into carbon and oxygen.
This pulsating white dwarf we discovered is extremely important since we can use the binary motion and the eclipse to independently measure the mass and radius of this white dwarf, which helps us determine what it 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.”Dr. Steven Parsons, Department of Physics and Astronomy, University of Sheffield