An Interstellar Origin for the Beryllium 10 in Calcium‐rich, Aluminum‐rich Inclusions
Why this work is in the frame
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Bibliographic record
Abstract
Beryllium 10 is a short-lived radionuclide (t1/2 = 1.5 Myr) that was incorporated live into calcium-rich, aluminum-rich inclusions (CAIs) at the birth of our solar system. Beryllium 10 is unique among the short-lived radionuclides in that it is formed only by spallation reactions and not by nucleosynthesis, e.g., in a supernova. Recent work by McKeegan, Gounelle, and others has stated that the high initial abundance of 10Be in CAIs (10Be/9Be ≈ 1 × 10-3) cannot be attributed to galactic cosmic rays (GCRs) and therefore concluded that the spallation reactions must have occurred within the solar nebula itself, because of energetic particles emitted by the early Sun. In this paper we reexamine this conclusion. We calculate the contributions of GCRs to the 10Be abundance in a molecular cloud core as it collapses to form a protostar and protoplanetary disk. We constrain the flux of protons and 10Be GCRs in the Sun's molecular cloud core 4.5 Gyr ago. We use numerical magnetohydrodynamic simulations of star formation to model the time evolution of the magnetic field strength and column density of gas in a collapsing cloud core. We account for magnetic focusing and magnetic mirroring and the anisotropic distribution of GCR pitch angles in the cloud core. We calculate the rates at which GCR protons and α-particles induce spallation reactions producing 10Be atoms, and the rates at which GCR 10Be nuclei are trapped in the cloud core. Accounting also for the decay of 10Be over the evolution of the cloud core, we calculate the time-varying 10Be/9Be ratio. We find that at the time of protostar formation 10Be/9Be ≈ 1 × 10-3, with an uncertainty of about a factor of 3. Spallation reactions account for 20% of the 10Be in CAIs, while trapped GCR 10Be nuclei account for the other 80%. The initial abundance of 10Be in CAIs is therefore entirely attributable to cosmic rays. We discuss the implications of this finding for the origin of other short-lived radionuclides and for the use of 10Be as a chronometer.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it