  We introduce a new imaging analysis technique to study the spatial
distribution of the X-ray emission from the hot bubble of planetary nebula
BD+30 3639. Hot bubble emission is typically photon-starved, thus limiting the
methods for spatial-spectral analysis, however, this new technique uses the
statistics of photon energies across the nebula to identify spatial variations.
Using the median energy value of the X-ray photons, we identified a rise in
median energy values towards the projected edge of the nebula, which we refer
to as radial spectral hardening. We explored the origin of this radial spectral
hardening with X-ray spectral analysis of distinct regions of high- and
low-median energy values. Given that the hot bubble is embedded within a young,
dense, planetary nebula, we argue that the radial spectral hardening is due to
an increased column density at the projected nebular edge. Median energy
imaging provides a promising new methodology for exploring the spatial
variations in faint extended X-ray sources.
