Computer simulations by researchers at the Indian Institute of Science suggest that white dwarfs with sufficiently strong internal magnetic fields could exceed the Chandrasekhar limit, the long-standing upper mass boundary of approximately 1.4 times the Sun's mass.
In one simulation, a magnetized carbon-oxygen white dwarf reached approximately 2.4 times the mass of the Sun. Without magnetic effects included, a comparable model reached only the conventional limit of roughly 1.4 solar masses. The team modified the stellar evolution program STARS to account for magnetic fields and white dwarf cooling, then simulated how magnetized stars change from the main-sequence stage through their final state as white dwarfs and beyond.
The simulations revealed that even a relatively weak magnetic field can become increasingly influential as a white dwarf accumulates matter from a companion star. As material builds up and the star contracts under its own gravity, compression strengthens the internal magnetic field, which provides additional pressure that counteracts gravity. This stronger magnetic support allows the white dwarf to hold more mass than would otherwise be possible.
"The important question was not simply whether a super-Chandrasekhar white dwarf is possible, but whether a star can actually evolve into one," says Zenia Zuraiq, first author of the study and PhD student at the Department of Physics. "Our simulations allowed us to follow that evolutionary pathway from the main-sequence star to the white dwarf, and show that under certain conditions, such a pathway is possible."
Astronomers have observed Type Ia supernovae that shine much more brightly than expected, raising the possibility that some white dwarfs may reach masses as high as 2.8 times that of the Sun before exploding. Type Ia supernovae serve as standardizable candles for measuring cosmic distances. If white dwarfs can reach substantially different masses due to magnetic fields, their resulting supernovae could have different properties and luminosity, potentially helping explain unusually bright Type Ia explosions and refining measurements of cosmic expansion.