Santa Cruz of Tenerife – Research led by the University of Sheffield (United Kingdom) and with the participation of the Canary Islands Astrophysics Institute (Spain) has discovered an ancient pulsating star in a double star system, which will give information on how stars like us evolve and die Sun.
The Institute of Astrophysics of the Canary Islands (IAC) reported on Monday that the discovery of the first pulsating white dwarf in an eclipsing binary system has been carried out using the HiPERCAM instrument of the Gran Telescopio Canarias at the Roque de los Muchachos Observatory ( Garafía, island of La Palma).
The finding has been published in the journal Nature Astronomy and the IAC has indicated that this type of binary, or double star system, is made up of two stars that orbit each other and periodically pass in front of each other, seen from Earth. .
One of the stars in the observed system is a white dwarf, the remnant that remains when a star like the Sun runs out of nuclear fuel, and thanks to this finding, scientists can see in detail, for the first time, how the evolution of the binary has affected the internal structure of a white dwarf.
The IAC indicates that determining what a white dwarf is made of is not easy, and explains that these are objects that have about half the mass of the Sun compressed to approximately the size of Earth, so gravity is extremely strong, about a million times larger than on our planet.
In this way, on the surface of a white dwarf an average person would weigh around 60,000,000 kilograms.
Gravity causes all of the white dwarf’s heavy elements to sink in the center, leaving only the lightest elements on the surface, so the true composition of the dwarf remains hidden underneath, -explains Steven Parsons, a researcher at the Physics Department. and Astronomy from the University of Sheffield.
To investigate the hidden structure of the white dwarf, scientists used different techniques. “This pulsating star is extremely important as we can use the motion and eclipse of the binary to independently measure its mass and radius, which helps us determine what it is made of,” says Parsons.
Although most white dwarfs are believed to be composed primarily of carbon and oxygen, this white dwarf has surprised scientists because it is made primarily of helium.
The team assumes that this is due to its stellar companion interrupting its evolution before it had a chance to fuse helium with carbon and oxygen.
“The most interesting thing is that the two stars of this binary system have interacted with each other in the past, transferring material back and forth between them, so we can see how the evolution of the binary has affected the internal structure of the dwarf white, something that we have not been able to do before for this type of system, “adds the astronomer.
The scientists combined the study of eclipses with astrosismology, a technique that consists of measuring the speed with which sound waves travel through the white dwarf.
To observe the star’s rapid and subtle pulsations, they used HiPERCAM, a “revolutionary” high-speed camera developed by a team led by Vikram S. Dhillon, an astrophysicist at the University of Sheffield and an IAC affiliate researcher.
This instrument, installed in the Gran Telescopio Canarias (GTC) of the Roque de los Muchachos Observatory (Garafía, La Palma), can take a photo every millisecond in five different colors simultaneously.
“This exciting scientific discovery would not have been possible without combining the GTC’s high light-picking power with HiPERCAM’s high-speed, multi-color capability,” says Dhillon.
The next step in the investigation will be to continue observing the white dwarf to record as many pulsations as possible using HiPERCAM and the Hubble Space Telescope.
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