Stars

Introduction

Interior Structure

Nuclear Fusion

Hydrogen Fusion

Hydrogen Fusion Rate

PP Fusion Simulator

PP Simulator Results

CNO Fusion Simulator

CNO Simulator Results

Hydrogen Fusion Simulator

Hydrogen Simulator Results

Helium Fusion

Helium Fusion Rate

Helium Fusion Simulator

Carbon and Oxygen Fusion

Radiative Processes

Radiative Transport

Convective Transport

Polytropic Stars

Hertzsprung-Russell Diagram

HR Diagrams of Clusters

HR Diagrams of Nearest Stars

Protostars

Main-Sequence Stars

Red Giant Stars

Evolution Red Giant

The Gravitational Collapse of Stars

Binary Stars

Binary Stars and Stellar Masses

Binary Star Birth

Tables

Characteristics of the Sun

10 Brightest Stars within 10 pc

Energy Excess in Nuclei

Elemental Abundances

Stars

Energy Excess in Nuclei

Nuclear fusion in stars takes elements with a high rest mass per nucleon and transforms them into elements with a low rest mass per nucleon (proton or neutron). In the table given below, the rest mass excess per nucleon is given for elements of different charge and atomic number. The values are given as an energy difference in MeV from the rest mass energy per nucleon of carbon-12.

In this table, the nuclei with charge and atomic numbers that are an integer multiple of helium-4's charge and atomic number are highlighted in red. Of the remaining atoms, those that are intermediate states of the proton-proton process of converting hydrogen into helium are highlighted in green. The remaining atoms that are involved in the CNO cycle for the conversion of hydrogen into helium are highlighted in blue.

This table highlights several points about the elements that impacts nuclear fusion within stars. First, the largest excess is in hydrogen, at 7.3 MeV, and the greatest energy release is in conversion of hydrogen into helium, which releases 6.7 MeV of energy per nucleon. The next point is that elements that are multiples of the helium charge and atomic number are energetically favored over other isotopic states. The final point is that the energy per nucleon in beryllium-8 is slightly less that the energy per nucleon in helium-4, which makes beryllium-8 unstable to decay into two helium atoms. Go to the table.

Rest Mass Excess