No Stellar Explosion Needed

Abstract

Planetary Science![Figure][1] CREDIT: NASA/JPL/UNIVERSITY OF ARIZONA The presence of the decay products of short-lived radioactive isotopes in meteorites provides clues to the astrophysical context of the formation of our solar system. Iron-60, for example, can only be produced in stellar explosions; given its half-life of 2.62 million years, a high abundance of this radioisotope in early solar system materials would imply that a star exploded in the vicinity of the newborn Sun. The abundance of 60Fe, an extinct radioisotope, can be constrained by measuring isotopic variations in its decay product 60Ni: a stable isotope of nickel. Previous estimates disagree, depending on the materials analyzed, which has been interpreted as reflecting heterogeneous distribution of 60Fe among planetary bodies. Based on high-precision and high-accuracy 60Ni and 58Fe isotope measurements of a variety of meteorites, Tang and Dauphas now show that, contrary to previous results, the initial abundance of 60Fe in the early solar system was uniformly low, precluding the need for a nearby stellar explosion around the time the solar system formed. Instead, 60Fe may have been inherited from the interstellar medium as the result of the long-term chemical evolution of our galaxy. Earth Planet. Sci. Lett. 359-360 , 248 (2012). [1]: pending:yes