A body is said to be at absolute zero if its temperature is 0K or -273.15 C.
At temperature T a body emits electromagnetic radiation at a rate `P = sigma*T^4` where P is the power per unit area, T is the temperature of the body in Kelvin and `sigma = 5.67×10^-8 W/(m^2*K^4)` which known as the Stefen-Boltzmann constant.
If a body is at temperature T, the wavelength at which the intensity of radiation per unit wavelength is maximum is given by `lambda = b/T` where `b = 2.8977721×10^-3 K*m` .
If the temperature of any substance is lowered to absolute zero, it does not emit any electromagnetic radiation. If T = 0 in the equation, `P = sigma*0^4` , P = 0. The power emitted by the substance is 0.