Energy density of the seed photons as a function of the distance from the pulsar. The dust emissivity was modelled to be confined in a shell surrounding the optical nebula. As a comparison, a composite of X-ray (Chandra: blue, white)/optical(HST: purple)/ infrared (Spitzer: pink) composite image from the nebula is shown with approximately matching spatial scale. Background image credit: X-ray: NASA/CXC/SAO; Optical: NASA/STScI; Infrared: NASA-JPL-Caltech).