A tidally destructed massive planet as the progenitor of the two light planets around the sdB star KIC 05807616

TL;DR

This paper proposes that two Earth-sized planets orbiting the sdB star KIC 05807616 are remnants of a tidally disrupted massive planet's core, formed after the planet's gaseous envelope was stripped during its inward spiral into its star.

Contribution

It introduces a novel scenario where a massive planet's core survives tidal destruction and forms multiple Earth-like planets around an EHB star, explaining their current orbits and properties.

Findings

Two Earth-sized planets likely originate from a tidally disrupted planetary core.

The planets may have magnetic fields ten times stronger than Earth's.

Survivability against UV radiation is enhanced by strong planetary magnetic fields.

Abstract

We propose that the two newly detected Earth-size planets around the hot B subdwarf star KIC 05807616 are remnant of the tidally destructed metallic core of a massive planet. A single massive gas-giant planet was spiralling-in inside the envelope of the red giant branch star progenitor of the extreme horizontal branch (EHB) star KIC 05807616. The released gravitational energy unbound most of the stellar envelope, turning it into an EHB star. The massive planet reached the tidal destruction radius of ~Ro from the core, where the planet's gaseous envelope was tidally removed. In our scenario the metallic core of the massive planet was tidally destructed into several Earth-like bodies immediately after the gaseous envelope of the planet was removed. Two, and possibly more, Earth-size fragments survived at orbital separations of >Ro within the gaseous disk. The bodies interact with the disk and among themselves and migrated to reach orbits close to a 3:2 resonance. These observed planets can have a planetary magnetic field about ten times as strong as that of Earth. This strong magnetic field can substantially reduce the evaporation rate from the planets and explain their survivability against the strong UV radiation of the EHB star.