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An international group of astrophysicists from the USA, the UK and Canada found that over time in the core of a white dwarf, which would become the Sun at the end of his life, will begin the process of crystallization of ions of carbon and oxygen. This process will free up a significant amount of heat and will stop the cooling of the stars for a billion years. Article researchers published in the journal Nature.
White dwarfs are the final stage of the evolution of main sequence stars, which include the Sun. The density of matter in the core of a white dwarf is about ten million grams per cubic centimeter. If such extreme values of the electron shell of the atoms disintegrate and matter is a plasma of electrons and nuclei. The Pauli principle forbids two electrons with the same spin to occupy a quantum state that creates a barrier to further compress the star. Thus, the gravitational collapse is impeded by the pressure of the degenerate electron gas.
It is believed that the cooling of white dwarfs in the core begins to occur crystallization of ions. The duration of this process depends on the mass of the star that is more massive white dwarf crystallization occurs earlier. Around the same time there is another process that connects the degenerate core and the outer shell, which contributes to the dissipation of energy released during solidification. About 50 years ago, scientists suggested that heavier white dwarfs (weighing more than 0.7 solar masses), the crystallization must begin earlier than the convective bondage that affects the physical properties of stars. However, until now evidence for the existence of this effect has been received.
Astrophysicists have analyzed photometric and astrometric data obtained by the Gaia space telescope, of white dwarfs located within 100 parsecs (326 light years) from the Sun. Just was studied 15 109 objects for which it was determined the temperature and the surface gravity, mass, and composition of the atmosphere. Scientists have built the diagram of Hertzsprung-Russell showing the relationship between absolute magnitude and spectral class (color) of stars.
Scientists have discovered a cross-sequence of white dwarfs, which are characterized by small absolute magnitude, and the discrepancy between age and degree of cooling. They correspond to the model according to which crystallization leads to the release of heat slows down the cooling process. According to one of the authors — physics of Pierre-Emmanuel Tremblay (Pier-Emmanuel Tremblay) from Warwick University (England), first obtained evidence that white dwarfs are really into the solid state.
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