Chandra constraints on the thermal conduction in the intracluster plasma of A2142

In this Letter, we use the recent Chandra observation of Abell 2142 reporte d by Markevitch ct al, to put constraints on thermal conduction in the intr acluster plasma. We show that the observed sharp temperature gradient requi res that classical conductivity has to be reduced at least by a factor of b etween 250 and 2500. The result provides a direct constraint on an importan t physical process relevant to the gas in the cores of clusters of galaxies .