After a short review of derivation of Hawking radiation by the
tunneling method, a quantum field theoretical approach, in which
 a quantum probe is used to unveil the intrinsic temperature
associated with stationary space-times with horizons is  
presented. The probe is identified with a conformally coupled
massless scalar field defined on a space-time with horizon and
the procedure to measure the local temperature is realized by
the use of Unruh-DeWitt detector. Another proposal to determine
local temperature, due to Buchholz is also considered.