Astrogeology

A Link Between Rocky Exoplanet Composition And Stellar Age

By Keith Cowing
Status Report
astro-ph.EP
November 27, 2024
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A Link Between Rocky Exoplanet Composition And Stellar Age
Rocky planet density and composition depends on the age of the host star. The mass and radius of small planets, colour-coded by age, alongside composition tracks from Zeng et al. (2016). The upper, light orange line corresponds to a planet with composition of 100% MgSiO3, i.e. 100% rocky mantle. The middle, dark orange line corresponds to a planet with 67.5% MgSiO3, and 32.5% Fe, providing an analogue for Earth-like composition. The lower blue line represents planets which would be composed of 100% Fe, essentially pure iron cores. — astro-ph.EP

Interior compositions are key for our understanding of Earth-like exoplanets. The composition of the core can influence the presence of a magnetic dynamo and the strength of gravity on the planetary surface, both of which heavily impact thermal and possible biological processes and thus the habitability for life and its evolution on the planet.

However, detailed measurements of the planetary interiors are extremely challenging for small exoplanets, and existing data suggest a wide diversity in planet compositions. Hitherto, only certain photospheric chemical abundances of the host stars have been considered as tracers to explain the diversity of exoplanet compositions.

Here we present a homogeneous analysis of stars hosting rocky exoplanets, with ages between 2 and 14 Gyr, revealing a correlation between rocky exoplanet compositions and the ages of the planetary systems. Denser rocky planets are found around younger stars. This suggests that the compositional diversity of rocky exoplanets can be linked to the ages of their host stars.

We interpret this to be a result of chemical evolution of stars in the Milky Way, which modifies the material out of which stars and planets form. The results imply that rocky planets which form today, at similar galactocentric radii, may have different formation conditions, and thus different properties than planets which formed several billion years ago, such as the Earth.

Angharad Weeks, Vincent Van Eylen, Daniel Huber, Daisuke Kawata, Amalie Stokholm, Victor Aguirre Børsen-Koch, Paola Pinilla, Jakob Lysgaard Rørsted, Mark Lykke Winther, Travis Berger

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2411.17358 [astro-ph.EP] (or arXiv:2411.17358v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2411.17358
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Submission history
From: Angharad Weeks
[v1] Tue, 26 Nov 2024 12:01:22 UTC (1,047 KB)
https://arxiv.org/abs/2411.17358
Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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