IISc Study Shows Magnetic Fields Let White Dwarf Stars Grow Past Mass Limit

New simulations show that strong internal magnetic fields can let white dwarf stars grow much larger than previously thought possible. When dying stars use up their fuel, their leftover dense cores become white dwarfs. For ordinary white dwarfs, the maximum mass limit is about 1.4 times the mass of the Sun, known as the Chandrasekhar limit.

Findings And Methods

Researchers at the Indian Institute of Science found that a magnetised carbon-oxygen white dwarf can reach about 2.4 times the mass of the Sun. To test how these stars form, the team updated a computer code from the University of Cambridge called STARS. They added magnetic field effects and cooling to track stars from their main-sequence phase into white dwarfs, while also modeling a system where a white dwarf takes matter from a partner star.

How It Works

As the white dwarf pulls in extra matter, it shrinks and grows denser. This process makes its internal magnetic field much stronger. The stronger magnetic field creates extra pressure inside the star, which helps it fight its own gravity and hold more weight. Scientists have thought this might happen for decades, and observations of very bright Type Ia supernovae have also hinted that some white dwarf mass limits could reach as high as 2.8 times the solar mass.

Context

White dwarf stars represent the final evolutionary stage for most stars in the universe, including our own Sun. Understanding their mass limits helps astronomers better measure cosmic distances and study how stars live and die.