Mechanism of Continuum Spectrum

Radiation is produced via various processes (radiation processes). Emission mechanism of continuum radiation includes blackbody radiation, thermal bremsstrahlung, synchrotron radiation, and Compton scattering.

Blackbody radiation is that emitted from thermal materials and has continuous components with various wavelengths. Its spectrum is called blackbody spectrum. The blackbody spectrum, its shape and intensity, is determined only by the gas temperature, according to the Planck law, and has a peak at some wavelength.

Blackbody spectrum
Planck formula
Continuum spectra from an accretion disk


Bremsstrahlung is radiation () emitted by charged particles, such as electrons (), which are braking around other charged particles, such as protons (). Bremsstrahlung emitted from thermal electrons is called thermal bremsstrahlung (thermal radiation).

Thermal bremsstrahlung

Synchrotron radiation
Synchrotron radiation is radiation () emitted by charged particles, such as high energy electrons (), which spirally move around magnetic fields (). This is also called magnetic bremsstrahlung.

Synchrotron radiation

Compton scattering

Inverse Compton scattering
Compton scattering is a process, where a photon () collides an electron () to change its motion and energy.

In the usual Compton scattering, where a photon () collides with an electron (), the electron gains energy, while the photon loses energy to change an low energy photon with long wavelength ().

On the contrary, in the inverse Compton scattering, where a high energy electron () collides with a photon (), the electron loses energy, while the photon gains energy to change a high energy photon with short wavelength (). If they suffer from the inverse Compton scattering repeatedly, low energy infrared photons transform high energy optical, ultraviolet, and X-ray photons.

Compton scattering

Temperature is somewhat confused and complicated concept. Indeed, there are various kinds of temperature, such as, blackbody temperature, effective temperature, color temperature, brightness temperature, antenna temperature, and so on.

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