After a star completes the oxygen-burning process, its core is composed primarily of silicon and sulfur. If it has sufficiently high mass, it further contracts until its core reaches temperatures in the range of 2.7–3.5 GK (230–300 keV). At these temperatures, silicon and other elements can photodisintegrate, emitting a proton or an alpha particle. Silicon burning proceeds by photodisintegration rearrangement, which creates new elements by adding one of these freed alpha particles (the equivalent of a helium nucleus) per capture step in the following sequence (photoejection of alphas not shown):