  We report on the observation of thermal photons from an accelerated electron
via examination of radiative beta decay of free neutrons measured by the RDK II
collaboration. The emitted photon spectrum is shown to corroborate a thermal
distribution consistent with the dynamical Casimir effect. Supported by a
robust chi-squared statistic, we find the photons reside in a one-dimensional
Planck spectrum with a temperature predicted by the moving mirror model.
