Part III: The Crab Nebula at Four Wavelengths
Comparing the X-ray, optical, infrared, and radio images of the Crab shows that the nebula appears most compact in X-rays and largest in the radio.
This can be understood by following the history of energetic electrons produced by the neutron star.
Review these images which have been resized to place them roughly on the same scale. Click on the radiation to see the larger image of each.