Some of the universe's dead stars may be capable of growing far more massive than a famous limit in physics was thought to allow. New computer simulations suggest that powerful magnetic fields hidden inside these stellar remnants could help them withstand crushing gravity and reach extraordinary masses.

The discovery challenges a long-standing understanding of white dwarfs, the dense cores left behind when certain stars exhaust their nuclear fuel and shed their outer layers. Although these stellar remnants are roughly the size of Earth, they can contain as much mass as the Sun or even more.

For white dwarfs without strong magnetic fields or rapid rotation, physicists have long recognized an upper mass boundary of approximately 1.4 times the Sun's mass.…