# Could electrons tunnel into protons in a white dwarf and turn it into neutron star?

Just like the Sun, where hydrogen ions tunnel into each other to start fusion, which would be otherwise impossible with this level of kinetic energy, could electrons inside a white dwarf tunnel into protons and turn it into a neutron star? Actually I want to know if the Pauli Exclusion Principle can prevent quantum tunneling so I used a compact star as an example.

• There is no Coulomb barrier between an electron and a proton - they are attracted to each other, not repulsed. Jan 19 at 0:08
• @JonCuster: English is second probably third language but in any case I removed the sentence ;D Jan 19 at 0:25
• @user6780 - no problem, I'd hate to try and write a technical question in French or Dutch anymore... Jan 19 at 0:40

However, there are no free protons in a white dwarf interior, they are instead inside carbon and oxygen nuclei. The energy penalty to convert a proton to a neutron in these stable nuclei is even higher and the electrons need to be highly relativistic ($$\gamma \sim 10$$).