Inverse Compton Scattering

Consider starlight: <hn> ~ 2eV (l~6000A)

or 3K background photons, <hn> ~3x10 eV

then

= for stars

= for the 3K background, to produce X-rays. We need cosmic rays!!!

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Inverse Compton scattering requires a target radiation, ie a photon input is required to absorb energy from relativistic electrons and scatter up to X-ray energies. We calculate the gamma factors required for the electrons to produce X-rays from stars and the 3K microwave background.

Because, in IC scattering,

gamma^2 ~ (final photon energy / initial photon energy)

we calculate the gamma factors for stars and the 3K microwave background as shown.

Thus electrons with cosmic ray energies are required to upscatter photons with these energies.