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**Black-body radiation** (**thermal emission** or **thermal radiation**) is
electromagnetic radiation within and surrounding a body
in thermodynamic equilibrium at a constant, uniform temperature.
This produces a continuous spectrum (a continuum emission,
the **black-body spectrum**) whose shape is dependent only on the
temperature of the body.

Planck's law (Planck function) describes the spectrum:

I(ν,T) = 2hν^{3}/c^{2}× 1/(e^{hν/(kT)}-1)

- I(ν,T) is power per unit area per solid angle in normal direction.
- h - Planck constant.
- c - speed of light in a vacuum.
- k - Boltzmann constant.
- ν - frequency of the electromagnetic radiation.
- T - temperature of the body in kelvins.

The above equation represents an ideal case, i.e., assuming the
thermodynamic equilibrium and uniform temperature, but all materials
produce radiation associated with their temperature, perhaps rightly
called *thermal emission* or *thermal radiation*, and informally,
*black-body radiation*. The ideal case and its equation represent
a useful first approximation.

atmospheric temperature profile

black body (BB)

cosmic microwave background (CMB)

Compton scattering

continuous spectrum

continuum emission

earthshine

eclipse mapping

infrared (IR)

Planck function

power law

protoplanetary disk (PPD)

radiative forcing (RF)

secondary eclipse

spectral energy distribution (SED)

star formation rate (SFR)

shock wave

submillimeter galaxy (SMG)

stellar parameter determination

stellar temperature determination

synchrotron radiation

thermodynamic equilibrium (TE)

ultraluminous infrared galaxy (ULIRG)

Very Small Array (VSA)

Wien's displacement law