Presolar grains: a record of stellar nucleosynthesis and processes in interstellar space

Abstract

Overview Presolar grains give us a direct window into stellar nucleosynthesis and provide probes of processes in interstellar space and in the solar nebula. Known types of presolar grains originated in the winds or ejecta of stars that lived and died before the solar system formed. After presenting a short history of how presolar grains came to be recognized, we describe how to identify presolar grains, the techniques used to study them, and the various types of grains currently available for study. We then review what presolar grains can tell us about stellar nucleosynthesis, the environments around evolved stars and in the interstellar medium, and how they can be used as probes of conditions in the early solar system. Grains that predate the solar system In recent years, a new source of information about stellar nucleosynthesis and the history of the elements between their ejection from stars and their incorporation into the solar system has become available. This source is the tiny dust grains that condensed from gas ejected from stars at the end of their lives and that survived unaltered to be incorporated into solar system materials. These presolar grains (Fig. 5.1) originated before the solar system formed and were part of the raw materials for the Sun, the planets, and other solar-system objects. They survived the collapse of the Sun's parent molecular cloud and the formation of the accretion disk and were incorporated essentially unchanged into the parent bodies of the chondritic meteorites.