Some White Dwarfs Might be Older than Previously Thought

Some White Dwarfs Might be Older than Previously ThoughtA process that reheats some white dwarfs might mean they are much older than previously thought, indicating a potential need to recalculate the age of stellar populations such as the Milky Way.By Elizabeth Fernandez M ore than 97% of the stars in our Galaxy will end their lives with a whimper-slowly cooling as stellar remnants known as white dwarfs.The cooling of white dwarfs follows a pattern that was thought to be so predictable that the temperatures of white dwarfs are used to determine the age of surrounding stars.New findings, however, indicate this pattern may need revision [1].Predictions made by Antoine Bédard of the University of Warwick, UK, and his colleagues now indicate that some white dwarfs may undergo a process Schematic drawings of two mechanisms for white dwarf cooling.(Left) The white dwarf contains no or few impurities.The star freezes from the inside out, with the crystallization front radiating spherically from the center of the remnant.(Right) The white dwarf contains many impurities.As crystals form, they float upward, displacing heavier impurity-containing liquid.This process sets up convection currents that reheat the dead star.