Extrasolar Refractory-Dominated Planetesimals: an Assessment

TL;DR

This study investigates why refractory-dominated planetesimals are not observed around white dwarfs, suggesting they are destroyed during stellar evolution or rarely blended with other bodies, with limited observational evidence for their existence.

Contribution

It provides an assessment of the absence of refractory-dominated planetesimals in white dwarf pollution data and proposes stellar evolution as a destruction mechanism.

Findings

No intact refractory-dominated planetesimals detected around white dwarfs

Such objects are likely destroyed during the star's Asymptotic Giant Branch phase

Weak evidence for blending of scattered refractory planetesimals with other bodies

Abstract

Previously published observations of 60 externally-polluted white dwarfs show that none of the stars have accreted from intact refractory-dominated parent bodies composed mainly of Al, Ca and O, although planetesimals with such a distinctive composition have been predicted to form. We propose that such remarkable objects are not detected, by themselves, because, unless they are scattered outward from their initial orbit, they are engulfed and destroyed during the star's Asymptotic Giant Branch evolution. As-yet, there is at most only weak evidence supporting a scenario where the composition of any extrasolar minor planet can be explained by blending of an outwardly scattered refractory-dominated planetesimal with an ambient asteroid.