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

Abstract

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 break-up of the parent planet to planetesimals near the tidal radius of about 1Rsun. Internal stress forces keep the planetesimal from further tidal break-up when their radius is less than about 100km. 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 daughter-planets from a planet (DPP) and the RPN scenarios are of speculative nature. More detail studies must follow to establish whether the suggested scenarios can indeed take place.