The Age of the Galaxy, Extreme Physics, Extra-Solar Planets and other Wisdom from the White Dwarf Stars

Don Winget

Often the simplest tools are the most powerful; this is true of the white dwarf stars. The evolution of the white dwarf stars is dominated by cooling; the coldest white dwarf stars are useful, independent, chronometers which give us clues to the age and star formation history of the Milky Way. We can calibrate these chronometers and probe the diverse and extreme physical conditions of their interiors using the techniques of asteroseismology.

The complex pulsators yield a bonanza of asteroseismological data. We are just beginning to explore the best ways of interpreting this information to place important constraints on the interior structure and physics, including chemical composition, reaction rates, plasmon neutrino energy production, and ion crystallization.

The simplest white dwarf pulsators are not asteroseismologically rich, except as an ensemble, yet they are important in a very different way. They are the most stable type of pulsating star known in frequency and phase, and make extremely accurate clocks. Slow drifts in pulsation frequencies reveal evolutionary cooling on timescales of Gigayears, and also serve as a useful tool for a sensitive search for extrasolar planets.

We will look at key progress and problems in these areas and assess the prospects for the future.