  We propose a method to study the degeneracy of a trapped atomic gas of
fermions through the relaxation of the motion of a test particle. In the
degenerate regime, and for an energy of the test particle well below the Fermi
energy, we show that the Fermi-Dirac statistics is responsible for a strong
decrease of the relaxation rate. This method can be used to directly measure
the temperature of the fermionic gas.
