Characterizing the nucleus of comet 162P/Siding Spring using ground-based photometry
Bibliographic record
Abstract
ABSTRACT Comet 162P/Siding Spring is a large Jupiter-family comet with extensive archival lightcurve data. We report new r-band nucleus light curves for this comet, acquired in 2018, 2021, and 2022. With the addition of these light curves, the phase angles, at which the nucleus has been observed, range from 0.39○ to 16.33○. We absolutely calibrate the comet light curves to r-band Pan-STARRS 1 magnitudes, and use these light curves to create a convex shape model of the nucleus by convex lightcurve inversion. The best-fitting shape model for 162P has axis ratios a/b = 1.56 and b/c = 2.33, sidereal period P = 32.864 ± 0.001 h, and a rotation pole oriented towards ecliptic longitude λE = 118○ ± 26○ and latitude βE = −50○ ± 21○. We constrain the possible nucleus elongation to lie within 1.4 < a/b < 2.0 and discuss tentative evidence that 162P may have a bilobed structure. Using the shape model to correct the light curves for rotational effects, we derive a linear phase function with slope β = 0.051 ± 0.002 mag deg−1 and intercept Hr(1, 1, 0) = 13.86 ± 0.02 for 162P. We find no evidence that the nucleus exhibited an opposition surge at phase angles down to 0.39°. The challenges associated with modelling the shapes of comet nuclei from light curves are highlighted, and we comment on the extent to which we anticipate that Legacy Survey of Space and Time will alleviate these challenges in the coming decade.
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".