Population synthesis of exoplanets accounting for orbital variations due to stellar evolution

TL;DR

This study uses population synthesis to model how exoplanet orbits change during late stellar evolution, revealing most planets are absorbed by their stars, with a small fraction ejected, estimating around 300 million ejected planets in the Milky Way.

Contribution

It introduces a comprehensive population synthesis approach to analyze exoplanet orbital evolution during stellar transformation into white dwarfs, considering Galactic star formation history.

Findings

Approximately 60% of planets are absorbed by parent stars.

Less than 1% of planets are ejected due to stellar wind mass loss.

Estimated 300 million ejected planets in the Milky Way.

Abstract

In this paper, the evolution of exoplanet orbits at the late stages of stellar evolution is studied by the method of population synthesis. The evolution of stars is traced from the Main Sequence stage to the white dwarf stage. The MESA package is used to calculate evolutionary tracks. The statistics of absorbed, ejected, and surviving planets by the time of the transformation of parent stars into white dwarfs are calculated taking into account the change in the rate of star formation in the Galaxy over the entire time of its existence. Planets around stars in the range of initial masses 1-8 $M_\odot$ are considered since less massive stars do not have time to leave the Main Sequence during the lifetime of the Galaxy, and more massive ones do not lead to the formation of white dwarfs. It is shown that with the initial $a$~--~$M_\mathrm{pl}$ distribution of planets adopted in this work, most (about 60\%) of the planets born from stars in the mass range under study are absorbed by their parent stars at the giant stage. A small fraction of the planets (less than one percent) are ejected from their systems because of the mass loss due to the stellar wind. The estimated number of ejected planets with masses ranging from 0.04 Earth masses to 13 Jupiter masses in the Milky way is approximately equal to 300 million.