Enhanced lithium depletion in Sun-like stars with orbiting planets

TL;DR

This study shows that Sun-like stars with orbiting planets have significantly lower lithium levels than similar stars without detected planets, suggesting planets influence stellar lithium depletion.

Contribution

It provides the first unbiased comparison of lithium abundances in stars with and without planets, revealing a link between planetary presence and lithium depletion.

Findings

Planet-hosting stars have less than 1% of primordial lithium.

Stars without detected planets have about 10 times more lithium.

Planet presence may enhance mixing and lithium burning in stars.

Abstract

The surface abundance of lithium on the Sun is 140 times less than protosolar, yet the temperature at the base of the surface convective zone is not hot enough to burn Li. A large range of Li abundances in solar type stars of the same age, mass and metallicity is observed, but theoretically difficult to understand. An earlier suggestion that Li is more depleted in stars with planets was weakened by the lack of a proper comparison sample of stars without detected planets. Here we report Li abundances for an unbiased sample of solar-analogue stars with and without detected planets. We find that the planet-bearing stars have less than 1 per cent of the primordial Li abundance, while about 50 per cent of the solar analogues without detected planets have on average 10 times more Li. The presence of planets may increase the amount of mixing and deepen the convective zone to such an extent that the Li can be burned.