Protoplanetary systems in distant star-forming regions as seen in maser lines

Proto-planetary disks emitting in the radio lines of complex molecules are found in many star-forming regions around high-density neutral cores of dust and gas. It seems that at present there is no other means of detecting very distant planetary bodies except by their molecular maser emission. The thermal emission from such objects would be strongly masked by the emission from surrounding hot dust. New properties of methanol maser lines which are supposed to be formed by protoplanets are discussed. A mass of the central protostar in 11 dense cores with Keplerian disk containing such protoplanets is obtained.