IISc study says strong magnetic fields could allow white dwarfs to grow beyond the Chandrasekhar limit

An Indian Institute of Science (IISc) study suggests strong magnetic fields could enable some white dwarfs to surpass the Chandrasekhar limit, a longstanding mass constraint. When a star exhausts its fuel and sheds its outer layers, a dense stellar remnant called a white dwarf is left behind. Typically, non-magnetized white dwarfs cannot exceed about 1.4 times the mass of the Sun. However, IISc researchers found that a magnetized carbon-oxygen white dwarf can reach roughly 2.4 solar masses.

Professor Banibrata Mukhopadhyay, the study's corresponding author, explained that the idea emerged in 2011 when a summer student approached him with a casual question about the impact of magnetic fields on the Chandrasekhar limit. The researchers used a modified computer model to track the evolution of white dwarfs with magnetic fields from the main sequence to their white dwarf fate.

They discovered that under certain conditions, a white dwarf could evolve into a "super-Chandrasekhar" status, challenging the traditional mass limit.

Zenia Zuraiq, the study's first author, noted that while the possibility of super-Chandrasekhar white dwarfs has been theorized for decades, the critical question was whether a star could actually evolve into such a massive white dwarf. By incorporating magnetic field effects and white dwarf cooling into the STARS code, the team was able to model this evolutionary pathway.

As the white dwarf accumulated additional mass from a companion star, its magnetic field strengthened over time. This additional pressure within the star could counteract its immense gravity, allowing it to support greater mass than previously thought possible.