Observations of the universe’s expansion created discussion regarding dark energy. There is consensus that late stage expansion currently is more linear than the equation R=r0*(t/t0)^(2/3). Since this equation represents conversion of kinetic energy to potential energy and is a curve, Hubble data showing that late stage expansion is almost linear appears to violate energy conservation and require a dark (unknown) energy source. Two literature proposals (cosmological constant and quintessence) attempt to account for this unknown energy source. This paper presents calculations indicating that energy produced by stars causes the linear expansion curve. The analysis draws on data regarding the relative abundance of elements to determine the number of stars and their energy output. A calculation procedure for expansion was developed that allows one to add energy and predict its effect on late stage expansion. It was surprising that a small amount of energy has a large effect on expansion. At the same time, the required energy addition has only a small effect on current temperature (2.73K). Energy produced by stars is fusion energy and provides a physical alternative to dark energy. Current cosmology is based on mass with kinetic energy but includes a large fraction (0.719) of dark energy. The expansion curve, energy release points and associated temperature curve is presented. Analysis shows that although the density is 9.14e-27 kg/m^3, the mass fractions should be 0.5 normal and 0.5 dark.