frequency is measured in radio and visible light.
   The blue-green and yellow areas indicate x-ray emissions from the area immediately surrounding the nebula. At least part of this nebular x-ray emission is also synchrotron radiation, which draws its power from the energy that the pulsar loses as its rotation slows. 
    The regions of the Crab Nebula that emit x-ray synchrotron radia- tion are much smaller than those emitting radio synchrotron radia- tion (compare radio and x-ray images). This is because highly energetic electrons are required 
to produce x-rays, whereas lower- energy electrons produce radio waves. Only a fraction of the elec- trons in the nebula can produce x-rays.