Bibliographic record
Abstract
Although PN are well known for their ring-shape appearance, they in fact have a diverse range of morphologies. Using photographs that he took at the Lick Observatory, Curtis (1918) was the first to arrange PN into different classes based on their appearances. The origin of such diverse shapes has remained a mystery for a long time. For example, the well known Ring Nebula (NGC 6720) has an elliptical ring appearance. The most obvious interpretation is that this represents a three-dimensional hollow shell projected onto the sky. However, the actual observed surface brightness of the “hole” in comparison to the shell is too low (∽1:20) to be consistent with this model (Minkowski and Osterbrock, 1960). The observed intensity distribution is in fact more compatible with an open-ended toroid viewed end on (Khromov and Kohoutek, 1968). Although this model gives a good approximation to the observed image, the origin of such a toroid is not explained. The physical origin of the different morphologies of PN and how they evolve to such forms therefore represents one of the greatest challenges in PN research. Morphological classifications Curtis (1918) classified his sample of 78 PN into helical, annular, disk (uniform and centrally bright), amorphous, and stellar. Subsequent classification schemes often use similar descriptive forms: stellar, disk, irregular, ring, anomalous (Perek & Kohoutek, 1967); elliptical, rings, bipolar, interlocking, peculiar, and doubtful (Greig, 1971; Westerlund and Henize, 1967); and round, elliptical, and butterfly (Balick, 1987).
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 0.002 |
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".