**Inverse-Compton Scattering** (also known as **up-scattering**) is the same as [[Compton Scattering]]; however, the low-energy photon is scattered to a higher-energy by the electron. This process is important for the following astrophysical phenomena: - Sunyaev-Zeldovich effect in [[Galaxy Cluster|galaxy cluster]] studies, whereby photons from the [[Cosmic Microwave Background|CMB]] move through the hot gas surrounding a galaxy cluster, and are up-scattered to higher energies. - The accretion disk surrounding a [[Black Hole|black hole]] is presumed to produce a thermal spectrum. The lower energy photons produced from this spectrum are scattered to higher energies by relativistic electrons in the surrounding corona. This is surmised to cause the power law component in the X-ray spectra ($0.2 - 10 \; {\rm keV}$) of accreting black holes, as in [[Question 71|quasar spectrum]]. - The gamma-ray emission in [[Gamma Ray Burst|GRBs]] is also hypothesized to result from up-scattering within the ultra-relativistic jet. *(see [[Question 67#fireball model]])*