The additional pressure of white dwarf stars generated by net charges.

This article focuses on the impact of net positive electric charges on the upper-mass limit and internal pressure of white dwarf (WD) stars. Traditionally, the WD mass limit of about 1.44 solar masses is derived assuming a neutral, zero-temperature, degenerate Fermi electron gas. Using statistical mechanics, the study shows that at typical WD temperatures (10^4–10^7 K), a small fraction of electrons exceed the Fermi energy and can escape the star's gravity, leading to a net positive charge. This net charge generates a Coulomb repulsive pressure comparable to the electron degeneracy pressure, which can increase the WD's upper-mass limit and radius while decreasing its mass density. The findings align with previous theoretical and observational studies suggesting compact stars may carry net charges up to ~10^20 Coulombs, and the results approximate solutions to the modified Tolman–Oppenheimer–Volkoff equations for charged, spherically symmetric stars with homogeneous mass and charge distributions.