GONE IN A BLAZE OF GLORY: THE DEMISE OF COMET C/2015 D1 (<i>SOHO</i>)
Bibliographic record
Abstract
We present studies of C/2015 D1 (SOHO), the first sunskirting comet ever seen from ground stations over the past half century. The Solar and Heliospheric Observatory (SOHO) witnessed its peculiar light curve with a huge dip followed by a flareup around perihelion: the dip was likely caused by sublimation of olivines, directly evidenced by a coincident temporary disappearance of the tail. The flareup likely reflects a disintegration event, which we suggest was triggered by intense thermal stress established within the nucleus interior. Photometric data reveal an increasingly dusty coma, indicative of volatile depletion. A catastrophic mass loss rate of $\sim$10$^{5}$ kg s$^{-1}$ around perihelion was seen. Ground-based Xingming Observatory spotted the post-perihelion debris cloud. Our morphological simulations of post-perihelion images find newly released dust grains of size $a \gtrsim 10$ $\mu$m in radius, however, a temporal increase in $a_{\min}$ was also witnessed, possibly due to swift dispersions of smaller grains swept away by radiation forces without replenishment. Together with the fading profile of the light curve, a power law dust size distribution with index $\gamma = 3.2 \pm 0.1$ is derived. We detected no active remaining cometary nuclei over $\sim$0.1 km in radius in post-perihelion images acquired at Lowell Observatory. Applying radial non-gravitational parameter, $\mathcal{A}_{1} = \left(1.209 \pm 0.118 \right) \times 10^{-6}$ AU day$^{-2}$, from an isothermal water-ice sublimation model to the SOHO astrometry significantly reduces residuals and sinusoidal trends in the orbit determination. The nucleus mass $\sim$10$^{8}$--10$^{9}$ kg, and the radius $\sim$50--150 m (bulk density $\rho_{\mathrm{d}} = 0.4$ g cm$^{-3}$ assumed) before the disintegration are deduced from the photometric data; consistent results were determined from the non-gravitational effects.
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How this classification was reachedexpand
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 | 0.001 | 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 | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".