Abstract
The luminosity of white dwarf stars can be attributed to the cooling process of their degenerate cores. The simple relationship existing between their luminosity and their age, together with the lack of white dwarfs fainter than log (L/L⊙)≈−4.5, provides a method of measuring the age of the disk and consequently that of the Universe1,2. Winget et al.2 have derived an age of the galactic disk of 9.3 Gyr and have then found that the Universe is young: 10.3 Gyr. These values depend on the assumption that completely ionized carbon and oxygen (the most abundant elements in white dwarf interiors) are miscible in solid phase. It is possible, however, that completely ionized carbon and oxygen separate during the process of crystallization3,4. The consequences of this behaviour on the evolution of mass-accreting carbon–oxygen white dwarfs in stellar binary systems5–7 and on the cooling process of white dwarfs8,9 have been already described. Here, we attempt to show that a galactic disk'age of 15 Gyr cannot be excluded by the white dwarf observations if carbon anil oxygen are immiscible in solid phase.
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Garcja-Berro, E., Hernanz, M., Isern, J. et al. Properties of high-density binary mixtures and the age of the Universe from white dwarf stars. Nature 333, 642–644 (1988). https://doi.org/10.1038/333642a0
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DOI: https://doi.org/10.1038/333642a0
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