Formation of Super-Earths and Mini-Neptunes From Rings of Planetesimals
The solar system planetary architecture has been proposed to be consistent with the terrestrial and giant planets forming from material rings at ~1 au and ~5 au, respectively.
Here, we show that super-Earths and mini-Neptunes may share a similar formation pathway. In our simulations conducted with a disk alpha-viscosity of 4e-3, super-Earths accrete from rings of rocky material in the inner disk, growing predominantly via planetesimal accretion.
Mini-Neptunes primarily originate from rings located beyond the water snowline, forming via pebble accretion. Our simulations broadly match the period-ratio distribution, the intra-system size uniformity, and the planet multiplicity distribution of exoplanets. The radius valley constrains the typical total mass available for rocky planet formation to be less than 3-6 Earth masses.
Our results predict that planets at ~1 au in systems with close-in super-Earths and mini-Neptunes are predominantly water-rich. Though relatively uncommon, at ~1% level, such systems might also host rocky Earth-sized planets in the habitable zone that underwent late giant impacts, akin to the Moon-forming event.
Schematic view of where and how super-Earths and mini-Neptunes form. Planetesimal formation occurs at different locations in the disk, associated with sublimation and condensation lines of silicates and water. Planetesimals and pebbles in the inner and outer rings have different compositions, as indicated by the different color coding (a). In the inner ring, planetesimal accretion dominates over pebble accretion, while in the outer ring, pebble accretion is relatively more efficient than planetesimal accretion (b). As planetesimals grow, they migrate inwards, forming resonant chains anchored at the disk’s inner edge. After gas disk dispersal, resonant chains are broken, leading to giant impacts that sculpt planetary atmospheres and orbital reconfiguration (c). — astro-ph.EP
Sho Shibata, Andre Izidoro
Comments: 22 pages, 16 figures, accepted for publication in the Astrophysical Journal Letters
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2501.03345 [astro-ph.EP] (or arXiv:2501.03345v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2501.03345
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Related DOI:
https://doi.org/10.3847/2041-8213/ada3d1
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Submission history
From: Sho Shibata
[v1] Mon, 6 Jan 2025 19:24:45 UTC (4,880 KB)
https://arxiv.org/abs/2501.03345
Astrobiology,
