Bibliographic record
Abstract
Abstract The sizes of small planets are known to be bimodal, with a gap separating planets that have lost their primordial atmospheres (super-Earths) and the ones that retain them (mini-Neptunes). Here, we report evidence for another distinct population at smaller sizes. By focusing on planets orbiting around GK dwarfs inward of 16 days and correcting for observational completeness, we find that the number of super-Earths peaks around 1.4 Earth radii and disappears shortly below this size. Instead, a new population of planets (sub-Earths) appears to dominate at sizes below ∼1 Earth radius, with an occurrence that increases with decreasing size. This pattern is also observed in ultra-short-period planets. The end of super-Earths supports earlier claims that super-Earths and mini-Neptunes, planets that likely form in gaseous protoplanetary disks, have a narrow mass distribution. Sub-Earths, in contrast, can be described by a power-law mass distribution and may be explained by the theory of terrestrial planet formation. We therefore speculate that they are formed well after the gaseous disks have dissipated. The extension of these sub-Earths toward longer orbital periods, currently invisible, may be the true terrestrial analogs. This strongly motivates new searches.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".