Fission in White Dwarfs as a New Supernova Mechanism I

White dwarf stars cool and eventually begin to crystallize in their cores. The freezing temperature of this Coulomb plasma of ionized nuclei is proportional to Z^5/3 (nuclear charge Z) due to the high Coulomb energies, so the first solids that form in a C/O white dwarf may be greatly enriched in actinides. We estimate that the solids may be so enriched in actinides, especially uranium, that they could support a fission chain reaction. This reaction could ignite carbon burning and lead to the explosion of an isolated WD in a thermonuclear supernova (SN Ia). Our mechanism could potentially explain SN Ia with sub-Chandrasekhar ejecta masses and short delay times.