The exact mass limit for full carbon burning depends on several factors such as metallicity and the detailed mass lost on the asymptotic giant branch, but is approximately 8–9 M ☉. After carbon burning is complete, the core of these stars reaches about 2.5 M ☉ and becomes hot enough for heavier elements to fuse. Before oxygen starts to fuse, neon begins to capture electrons which triggers neon burning. For a range of stars of approximately 8–12 M ☉, this process is unstable and creates runaway fusion resulting in an electron capture supernova.