Researchers Discover the First Pulsating White Dwarf in a Binary Star System

​International research led by astronomers from the University of Sheffield and Instituto de Astrofísica de Canarias​ has found a pulsating star in a binary star system, which will enable them to gain important data of the way stars like our Sun develop and ultimately die.

The discovery of the first-ever pulsating white dwarf star in an eclipsing double star system suggests that the international team can gain some insight into how binary evolution has impacted the inner parts of a white dwarf in detail for the first time.

Researchers Have Access to Important Information Now

An eclipsing binary, also known as a double star system, is composed of two stars rotating around each other and regularly passing in front of each other as astronomers see it from Earth.

White dwarfs are torched cores left behind when a star like our Sun dies. This individual white dwarf could offer researchers crucial insights into the composition, development, and death of these stars for the first time. The majority of white dwarfs​ are believed to be composed mainly of carbon and oxygen, but this one is mostly made of helium.

The researchers believe this is a result of its pair stopping its evolution in the early stages before it got the possibility to merge the helium into carbon and oxygen. The pulsations from the star were found using HiPERCAM, an incredibly high-speed camera designed by a team led by Professor Vik Dhillon from the University of Sheffield’s Department of Physics and Astronomy.

HiPERCAM is able to capture one image every millisecond at the same time in five different colors and is attached to the 10.4-meter (34 feet) Gran Telescopio Canarias (GTC), the globe’s largest optical telescope on La Palma.

The camera made it possible for the researchers to identify the rapid and dim pulsations from this particular white dwarf.

Determining The Inner Structure of a White Dwarf

The pulsations of the white dwarf​ and the eclipsing double star system enabled the team to analyze the structure of it, applying two different methods, asteroseismology and eclipse data. Asteroseismology measures the speed of sound waves that travel through the white dwarf​.

Dr. Steven Parsons, from the University of Shieffield’s Department of Physics and Astronomy, also the author of the study, said: “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 60,000,000 kilograms (13,227,7357 pounds).”

He then continued explaining: “The gravity causes all of the heavy elements in the white dwarf to sink to the center, leaving only the lightest elements at the surface and so the true composition of it remains hidden underneath. 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.”

What is more interesting, according to Dr. Parsons, is that the two stars in the binary system have engaged with each other in the past, moving material back and forth between them. Scientists can see now the way this development has impacted the inner structure of the white dwarf, something they could not see all those years.

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