  The magnesium-potassium anti-correlation observed in globular cluster NGC2419
can be explained by nuclear burning of hydrogen in hot environments. The exact
site of this nuclear burning is, as yet, unknown. In order to constrain the
sites responsible for this anti-correlation, the nuclear reactions involved
must be well understood. The $^{39}$K+p reactions are one such pair of
reactions. Here, we report a new evaluation of the
$^{39}$K(p,$\gamma$)$^{40}$Ca reaction rate by taking into account ambiguities
and measurement uncertainties in the nuclear data. The uncertainty in the
$^{39}$K(p,$\gamma$)$^{40}$Ca reaction rate is larger than previously assumed,
and its influence on nucleosynthesis models is demonstrated. We find the
$^{39}$K(p,$\gamma$)$^{40}$Ca reaction cross section should be the focus of
future experimental study to help constrain models aimed at explaining the
magnesium-potassium anti-correlation in globular clusters.
