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13 January 2019, 08:11 | Ross Houston
An artist's illustration of a white dwarf in the process of solidifying. Credit University of Warwick Mark Garlick
Prior to crystallization, atoms are thought to be packed so tightly in the core of a white dwarf that their electrons become unbound, leaving a conducting electron gas and positively charged nuclei in a fluid form. To put that in perspective: A mere teaspoon of white-dwarf material would weigh about as much as an elephant, if you could somehow transport the stuff to our planet. What they found was a "pile-up", or a large group of stars at specific colors/luminosities that "do not correspond to any single mass or age".
"This is the first direct evidence that white dwarfs crystallize, or transition from liquid to solid", Tremblay said. They believe that the missing energy could be released in the form of gravitational energy, created as carbon is pushed to the surface of the star by falling oxygen that had crystallized earlier in the process.
White-dwarf crystallization is akin to water freezing from liquid to ice. Therefore, gaining a greater understanding of how crystallization can stave off the cooling process, essentially making the stars appear younger than they really are, would help astronomers improve the accuracy of the white dwarf dating technique.
In 10 billion years the sun will be a crystal.
It is assessed that at times these stars have backed off their maturing by as much as 2 billion years, or 15 percent of the age of our galaxy.
Astronomers chose 15,000 white dwarf candidates within around 300 light years of Earth from perceptions made by the Gaia satellite and broke down information on the stars' luminosities and colors. At some time in their evolution, all white dwarfs will crystallize with more massive ones dying faster than the small ones. Before it begins to solidify and harden gradually, the sun will turn into a red giant, and from that moment it will begin to shrink down and turn into a white dwarf. White dwarfs with lower masses, closer to the expected end stage of the Sun, cool in a slower fashion, requiring up to six billion years to turn into dead solid spheres. The process has already been completed by billions of white dwarfs in our galaxy, and in about 10 billion years the Sun will follow as well.
'The sun itself will become a crystal white dwarf in about 10 billion years'.
Dr Tremblay adds: "Not only do we have evidence of heat release upon solidification, but considerably more energy release is needed to explain the observations". Red dwarfs, the most common type of star, keep burning until they have transformed all their hydrogen into helium, turning into a white dwarf.
After this contraction the star can still create energy by fusing helium to create carbon and oxygen, Tremblay said. "This experiment on an ultra-dense matter is something that simply can not be performed in any laboratory on Earth".
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