A computer simulation study suggests that some white dwarfs could grow heavier than the famous Chandrasekhar limit if strong magnetic fields help support them against gravity. The model reached about 2.4 times the Sun’s mass in one case, well above the roughly 1.4-solar-mass limit used for white dwarfs without strong magnetic fields or rapid rotation.
The work, by researchers in the Department of Physics at the Indian Institute of Science (IISc) and collaborators, is described in a report attributed to IISc. The study’s first author, Zenia Zuraiq, is a PhD student in the department; corresponding author Banibrata Mukhopadhyay is a professor there. Their paper, with five coauthors, was published in The Astrophysical Journal Letters.
White dwarfs are the dense cores left behind when certain stars run out of nuclear fuel and shed their outer layers. Though roughly Earth-sized, they can contain as much mass as the Sun or more. The Chandrasekhar limit describes an approximate upper mass for white dwarfs without strong magnetic fields or rapid rotation. It matters because a carbon-oxygen white dwarf nearing that limit may ignite carbon and explode as a Type Ia supernova.
The researchers asked whether a star could evolve into a white dwarf above the conventional limit, rather than only whether such an object could theoretically exist. “The important question was not simply whether a super-Chandrasekhar white dwarf is possible, but whether a star can actually evolve into one,” Zuraiq said.
To explore that pathway, the team modified STARS, a stellar-evolution program originally developed at the University of Cambridge. They added calculations for magnetic fields and white dwarf cooling, then modeled a star’s evolution from its hydrogen-fusing main-sequence stage through to the white dwarf phase. The study also modeled a binary system, where the white dwarf gains material from a companion star, a process called accretion.
In one simulation, a carbon-oxygen white dwarf that began at 1.02 solar masses formed from a main-sequence star with eight solar masses. It then accumulated matter at a modeled rate of one-billionth of the Sun’s mass per year. With magnetic effects included, it reached about 2.4 solar masses. An otherwise comparable model without those effects reached roughly 1.4 solar masses.
The proposed mechanism is that as the white dwarf accumulates matter, it contracts under gravity and its internal magnetic field strengthens. The field’s pressure could provide additional support against gravity, allowing the star to hold more mass. The simulations also suggest that magnetic effects change the relationship between a white dwarf’s mass and size. The maximum mass could vary depending on how magnetic fields behave inside the star.
That possibility may be relevant to an astronomical puzzle: some observed white dwarfs have larger radii than conventional models predict for their relatively low masses. Magnetic pressure is one proposed explanation in the report, but the simulations do not establish that it accounts for those observations.
The result could also matter for interpreting Type Ia supernovae. Astronomers use these explosions as standardizable candles: comparing their peak brightness with how bright they appear from Earth helps estimate cosmic distances. The report notes that some Type Ia explosions are unusually bright, and that astronomers have considered whether their white dwarf progenitors might reach masses as high as 2.8 times the Sun’s mass. If some progenitors have substantially different masses and magnetic fields, those properties could affect the resulting explosions’ brightness.
The study offers a possible evolutionary route to unusually massive white dwarfs; it does not directly observe one growing to these masses. Whether real stars follow the modeled pathway, and whether it explains unusually bright Type Ia supernovae, remains an open question. The simulations point to magnetic fields as a factor worth accounting for when investigating how white dwarfs evolve and how their explosions are interpreted.
<a href="https://www.sciencedaily.com/releases/2026/11/261102202835.htm">Source: IISc report on massive white dwarfs</a>