Abundance and Origin of the Elements in the Sun

Abundance and Origin of the Elements in the Sun

. The abundance of the elements in the Sun, plotted as a function of their weight, on a logarithmic scale that spans twelve orders of magnitude, or one million million. Hydrogen, the lightest and most abundant element in the Sun, was formed 10 to 20 billion years ago in the immediate aftermath of the big-bang explosion that led to the expanding Universe. Most of the helium now in the Sun was also created then. All the elements heavier than helium were synthesized in the interiors of stars that no longer shine, and then wafted or blasted into interstellar space where the Sun subsequently originated. Carbon, nitrogen, oxygen and iron, were created over long time intervals during successive nuclear burning stages in former stars. Because any nuclear reaction involving the iron group must absorb energy rather than release it, these elements cannot serve as fuel in further chains of nuclear reactions inside stars. Elements heavier than iron, such as gold and uranium, were produced by neutron capture reactions during the supernova explosions of massive stars that lived and died before the Sun was born. The exponential decline of abundance with increasing mass can be explained by the rarity of stars that have evolved to later stages of life.

Copyright 2010, Professor Kenneth R. Lang, Tufts University