Our first news is related with the work done by Fouesneau, M., et al., and submitted recently to the AstroPhysical Journal. They propose a precise age determination method in the case of binary stars were one of the two components is a White Dwarf.
Stellar dating in the case of the most common stars, those similar to our Sun or smaller, is one of the most difficult tasks. Therefore, the presence of a “companion clock” in the form of a more easily aging star is a very god opportunity.
White Dwarfs (WD), the remaining compact nucleus of a low-mass-star after its “death”, cools-down with time following certain rules, known as cooling curves. Therefore, aging a WD only needs the knowledge of its distance, magnitude, colour, and atmospheric type. Thanks to Gaia, some of the difficulties determining these parameters disappear. In a binary system, we assume that both stars are born at the same time. Therefore, if in a binary system one of the components is a WD, its dating provides a precise dating of the component. This is a good procedure for dating Main-Sequence stars, that is, stars burning Hydrogen at their nucleus. This is the phase where a star spends most of its life and in which changes happen smoothly.
In their work, Fouesneau, M., et al. have aged up to 67 systems composed by a WD and a Main-Sequence star using, in particular, data from Gaia DR1, with precisions better than a 20%. These precisions are similar to those obtained with the other most precise techniques (asteroseismology and eclipsing binaries), confirming this technique as a very interesting alternative when the Main-Sequence star is companied by a WD.
Picture “White Dwarf” by Antza2