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

Researchers at the Indian Institute of Science (IISc) have demonstrated through simulations that strong magnetic fields could allow certain white dwarfs to exceed the traditional Chandrasekhar limit of around 1.4 solar masses. A white dwarf is the dense, Earth-sized remnant of a star that has exhausted its nuclear fuel. In their study, published in The Astrophysical Journal Letters, the team found that a magnetized carbon-oxygen white dwarf could potentially reach about 2.4 solar masses – significantly above the Chandrasekhar limit.

Banibrata Mukhopadhyay, the study's lead author and a physics professor at IISc, explained that the concept of a "super-Chandrasekhar" white dwarf had been proposed theoretically since 2011. Observations of unusually luminous Type Ia supernovae, which serve as cosmic distance markers, have further supported this idea, suggesting that progenitor white dwarfs could have masses up to 2.8 times that of the Sun.

The key question was whether a star could evolve into such a massive white dwarf. To investigate, the researchers modified an existing computer code, STARS, to account for magnetic fields and white dwarf cooling. This enabled them to simulate the evolution of magnetized stars from their main sequence phase to their final white dwarf stage.

The simulations also considered binary systems where the white dwarf accretes matter from a companion star. As the white dwarf gained mass, Mukhopadhyay noted that the magnetic field initially weak and becomes increasingly significant. As the star's mass increased and density rose, the magnetic field strengthened, providing additional support against the star's own gravity.

This altered the typical relationship between mass and size, establishing a new mass limit that depended on the specifics of the magnetic field's physics.