As time goes on, and the electrons move outward, they lose energy to radiation. The diffuse optical light comes from intermediate energy particles produced by the pulsar. The optical light from the filaments is due to hot gas at temperatures of tens of thousands of degrees. The infrared radiation comes from electrons with energies lower than those producing the optical light. Additional infrared radiation comes from dust grains mixed in with the hot gas in the filaments.
Radio waves come from the lowest energy electrons.
They can travel the greatest distance and define the full extent of the nebula. The Crab's central pulsar was discovered in 1968 by radio astronomers. The pulsar was then identified as a source of periodic optical and X-ray radiation. The periodic flashes of radiation are caused by a beam from the rapidly rotating neutron star .