Planetary systems and real planetary nebulae from planet destruction near white dwarfs

We suggest that tidal destruction of Earth-like and icy planets near a white dwarf (WD) might lead to the formation of one or more low-mass - Earth-like and lighter - planets in tight orbits around the WD. The formation of the new WD planetary system starts with a tidal breakup of the parent planet to planetesimals near the tidal radius of about 1RO˙. Internal stress forces keep the planetesimal from further tidal breakup when their radius is less than about 100 km. We speculate that the planetesimals then bind together to form new sub-Earth daughter-planets at a few solar radii around the WD. More massive planets that contain hydrogen supply the WD with fresh nuclear fuel to reincarnate its stellar-giant phase. Some of the hydrogen will be inflated in a large envelope. The envelope blows a wind to form a nebula that is later (after the entire envelope is lost) ionized by the hot WD. We term this glowing ionized nebula that originated from a planet a real planetary nebula (RPN). This preliminary study of daughterplanets from a planet and the RPN scenarios are of speculative nature. More detailed studies must follow to establish whether the suggested scenarios can indeed take place.