Aluminium-26 in the early solar system

Abstract

Until a few years ago, most scientists believed that the isotopic anomalies produced by the extinct radionuclides such as26Al and129I relative to normal abundances are all of the order of 10−4 despite the wide range in their mean lifetime and hence this anomaly range must be the result of inhomogenious mixing ofexotic materials with much larger quantities ofnormal solar system materials over a short time rather than the result of free decay. Re-examination of the existing aluminum isotope data for the mineral inclusions of the carbonaceous chondrite Murchison reveals, however, that the observed anomalies can be explained in a more straightforward manner as due to the formation of spallation-produced aluminum and magnesium isotopes from28Si during thex-process nucleosynthesis, which must have occurred on the surface of an exploding supernova more than 5 billion years ago.