Abstract: Planets and dwarf planets are always absorbing the energy emitted by the sun. Simultaneously,they are emitting energy by thermal radiation.Assuming that the bodies are in thermal equilibrium,the theoretical temperatures are obtained.The results show that the theoretical temperatures agree roughly with actual ones,and they depend on the distances from the sun,not on the sizes of the planets.Additionally,outer atmosphere and internal heat of some planets exert some effect on the temperatures.The surface maximum temperatures have been also calculated.The temperature after cooling has been also discussed.They agree well with actual ones for the objects without atmosphere.