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Published online by Cambridge University Press: 12 April 2016
A model of maser emission spots as icy planets orbiting young massive stars is proposed. It is argued that the interstellar gas phase abundance of methanol, H2O and OH is much too low to produce maser emission from small gas clumps. The interstellar grains, on the other hand, consisting mainly of water ice and several per cent of methanol, can produce a favorable environment for the maser emission when evaporated. Big comets or planets covered by the water/methanol ice orbiting young massive stars can be the sites of the maser emission. The ice evaporates under stellar radiation, and water and methanol molecules emit corresponding maser lines, while OH molecules are produced from dissociation of water by the stellar radiation. VLBI observations of masers in W 3(OH), W 75N and V645 Cyg show that proposed planets are found in disks, and are moving on Keplerian orbits around O, B-stars. In the case of the O-star in W 3(OH) the planets are located beyond the compact HII region of the star. Extended envelopes of the icy planets provide molecular abundance, gas temperature and density adequate for the maser emission.