The temperature and mass of the star indicate that its core is transforming into a solid and dense cosmic diamond. The research findings will be published in the Monthly Notices of the Royal Astronomical Society and are already available in the arXiv database, as reported by Science Alert on June 11th.
Illustration of the crystallization of the core of a white dwarf star into a diamond. Image: Harvard-Smithsonian Center for Astrophysics
The matter within the white dwarf star is tightly compressed, but it does not collapse into the core due to the degenerate electron pressure. Despite being faint, the star still emits light from the remaining heat. Over time, it will cool down and evolve into a black dwarf when it loses all of its thermal energy, transforming into a crystallized carbon mass. Estimates suggest that this process takes an incredibly long time, around a quadrillion years, while the universe itself is only 13.8 billion years old. Therefore, scientists can only determine the beginning of the crystallization signs within the core of a white dwarf star.
During the crystallization process, carbon and oxygen atoms inside the white dwarf star cease their free movement and form bonds, self-arranging into a crystal lattice. The energy released from this process dissipates as heat, slowing down the cooling activity of the white dwarf star and giving it an appearance that is “younger” than its actual age.
Led by international astronomers, including Alexander Venner from the University of Southern Queensland, Australia, the team utilized data from the Gaia observatory to explore multiple star systems. They discovered a white dwarf star influenced by the gravitational force of a triple-star system named HD 190412. The HD 190412 system was subsequently renamed 190412 C and became a quadruple-star system. The characteristics of the white dwarf star indicate that it is undergoing the process of crystallization. The density of the star is over one million kg/m³, while the density of diamond is 3,500 kg/m³.
The remaining three stars in the system allowed the research team to determine the age of the white dwarf star. The age of the star system is approximately 7.3 billion years, while the white dwarf star itself is 4.2 billion years old. The time difference of 3.1 billion years demonstrates that the crystallization process slows down the cooling time of the white dwarf star by one billion years. Its proximity to Earth suggests the possibility of many similar star systems existing in the universe.