| Term: | Urca process |
| Definition: |
A cycle of nuclear reactions, primarily among the iron group of elements, accompanied by a high rate of neutrino formation. Neutrinos carry away energy quickly leading to the cooling of the stellar core and a dramatic drop in the pressure. Due to this process in pre-supernova stars, the core becomes unable to support the weight of the overlying layers. These layers collapse onto the core and subsequently rebound and escape in the supernova explosion. |