Injection of newly synthesized elements into the protosolar cloud

The relatively high initial abundance of the short–lived radioisotope 26Al in calcium–aluminium–rich refractory inclusions found in meteorites is inconsistent with forming the 26Al by irradiation in the solar nebula, unless the inclusions are shielded from irradiation by a more volatile mantle. Nucleosynthesis of the 26Al in a stellar source, such as a supernova, remains a likely alternative explanation, coupled with rapid injection of the newly synthesized 26Al into the protosolar cloud. In order to retain the live 26Al, the protosolar cloud must then collapse to form the solar nebula in less than 1 Myr. These requirements lead to the hypothesis of the supernova–triggered collapse of the protosolar cloud and injection of supernova shock wave material into the cloud. Theoretical models of the interaction of interstellar shock waves with target protosolar clouds show that a distant supernova can both trigger collapse and inject ca. 10% of the shock wave material incident on the cloud through Rayleigh–Taylor fingers.