# WASP-80 b: Methane across a Cool Giant's Atmosphere
**Independent research report by [Biswajit Jana](https://biswajit1999.github.io/Biswajit_Jana.github.io/)** · [Live report](https://biswajit1999.github.io/wasp-80b-exoplanet-report/) · [ORCID](https://orcid.org/0009-0002-2411-1891) · [Complete research portfolio](https://biswajit1999.github.io/Biswajit_Jana.github.io/research/exoplanets/)
AI-generated artist's interpretation informed by the measured system properties; not a direct image.
**Warm Jupiter · methane chemistry · JWST context + TESS**
A comparatively cool transiting giant where JWST detected methane in both transmission and emission, paired with a reproducible TESS transit fit and evidence audit.
**[Open the full report](https://biswajit1999.github.io/wasp-80b-exoplanet-report/)** — the live GitHub Pages version.
## Data sources
- **System parameters** — the saved `pscomppars` row from the [NASA Exoplanet Archive TAP service](https://exoplanetarchive.ipac.caltech.edu/TAP/sync?query=select+pl_name%2Chostname%2Cra%2Cdec%2Cpl_orbper%2Cpl_tranmid%2Cpl_trandur%2Cpl_rade%2Cpl_bmasse%2Cpl_eqt%2Cpl_orbsmax%2Csy_dist%2Csy_tmag%2Cst_teff%2Cst_rad%2Cst_mass%2Cdisc_year%2Cdiscoverymethod%2Cdisc_refname%2Cdisc_pubdate%2Cdisc_facility+from+pscomppars+where+pl_name%3D%27WASP-80+b%27&format=csv).
- **Observed photometry** — unmodified MAST file `tess2022190063128-s0054-0000000243921117-0227-s_lc.fits`, TESS Sector 54, DOI [10.17909/t9-nmc8-f686](https://doi.org/10.17909/t9-nmc8-f686). This is a real SPOC reduced light curve, not simulated data.
- **Observed spectra** — Bell et al. (2023) JWST/NIRCam transmission and emission source data plus the supplied full, no-CH4, and no-H2O model contours, DOI [10.1038/s41586-023-06687-0](https://doi.org/10.1038/s41586-023-06687-0). The canonical derivative retains all 113 journal-workbook channels and carries source and output SHA-256 receipts.
- Exact URLs, IDs, retrieval date, and SHA-256 checksum are in [`data/SOURCE.md`](data/SOURCE.md).
## Reproduce the analysis
```bash
pip install -r requirements.txt
python scripts/prepare_spectral_data.py # explicit networked provenance replay
python scripts/analyze_transit.py
python scripts/analyze_multisector.py
python scripts/analyze_atmospheric_evidence.py
python scripts/analyze_methane_consistency.py
pytest tests/ -v
```
The script keeps finite `QUALITY == 0` cadences, normalizes `PDCSAP_FLUX`, and applies one symmetric robust outlier rule. A local linear null is compared with a circular quadratic-limb-darkened transit. The archive period and predicted phase are retained, while midpoint, radius ratio, impact parameter, baseline, and baseline slope are fitted inside a bounded window. The limb-darkening coefficients and scaled semi-major axis are fixed and disclosed in the CSV.
## What the corrected fit shows
| Quantity | Result |
|---|---:|
| TESS sector | 54 |
| Cadences in fitted window | 2026 |
| Transit support | ΔBIC ≥ 10 |
| Midpoint correction | -0.008 h ± 0.13 min |
| Model mid-transit depth | 34333.5 ± 146.3 ppm |
| Radius ratio Rp/Rs | 0.16762 |
| Fitted / published duration | 2.141 / 2.131 h |
| Linear null χ² / dof / BIC | 138012.01 / 2024 / 138027.24 |
| Transit χ² / dof / BIC | 4390.76 / 2021 / 4428.83 |
| ΔBIC (null − transit) | 133598.41 |
The timing-adjusted transit is strongly preferred by ΔBIC = 133598.4. Its fitted midpoint is -0.008 hours from the historical prediction; the model's mid-transit depth is 34333.5 ± 146.3 ppm. A fitted timing correction can diagnose ephemeris drift, but this single-sector fit is not a replacement for a global transit-timing analysis.
## Available-sector robustness and correlated noise
MAST exposes one SPOC time-series sector for the target in the queried result, S54. Its archive prediction was timing-adjusted and meets Delta BIC >= 10. The formal depth error was inflated by sqrt(max(reduced chi-square, 1)) times the residual time-averaging beta factor (3.82), giving 34333.5 +/- 559.3 ppm. A sector-to-sector Q test is impossible with one sector; the generated panel is retained as an explicit acquisition-limit diagnostic rather than evidence of cross-sector stability. These scaled errors are not a Gaussian-process noise model.
The per-sector table is in [`figures/multisector_statistics.csv`](figures/multisector_statistics.csv). Regenerate all three figures with `python scripts/analyze_multisector.py`.
## Atmospheric evidence: detection, limit, or unknown?
The Nature retrieval reports methane from both transmission and emission and water at differing significance. CO, CO2, NH3, and SO2 were included but not constrained in the narrow NIRCam band. This repository records the evidence hierarchy without pretending that TESS photometry can measure composition.
| Species | Status | Evidence | Basis |
|---|---|---|---|
| CH4 | reported detection | 6.1 sigma in transmission and emission | free atmospheric retrieval |
| H2O | reported detection | 4.6 sigma transmission; 2.6 sigma emission | free atmospheric retrieval |
| CO / CO2 / NH3 / SO2 | unconstrained | no abundance constraint | retrieval over 2.4-4.0 microns |
| O2 | no evidence | not reported | no molecular-oxygen inference |
Primary source: [Bell et al. 2023, Nature](https://doi.org/10.1038/s41586-023-06687-0). The table is also available as [`data/atmospheric_evidence.csv`](data/atmospheric_evidence.csv). Oxygen-bearing species such as H2O, CO2, and SO2 are **not** evidence for molecular oxygen (O2) or a biosignature.
## Published-curve methane morphology sensitivity audit
The journal source data support a narrower, reproducible question: does the
sign of the residual contrast between the supplied full and component-removed
CH4 curves depend on adjacent-channel bin width or origin? The canonical input
now retains all **113 native channels**. A frozen grid evaluates factors 1, 2,
4, 5, 8, and 10 at every possible integer origin: **30 designs per geometry**.
The contrast is positive in all 60 rows. It ranges from **63.17 to 85.74** in
transmission and **217.65 to 245.99** in emission; the smallest leave-one-bin-
out values across the complete grid are **39.80** and **154.20**.
These delta-chi-square values are intentionally **not converted to detection
sigma**. The public component-removed curves are posterior spectral
post-processing from a retrieval fitted to the same observations—not
independently refitted nested null models or validation data. The paper's
reported 6.1-sigma CH4 detections remain citation-only here. This calculation
shows binning-sign robustness of the supplied morphology, nothing more.
The published methane abundances, log10(CH4) = -4.2 (+0.5/-0.7) in transmission
and -3.9 (+0.6/-0.7) in emission, differ by only **0.34 sigma** under a simple
symmetrized independent-error comparison. Using the saved composite planet and
star values gives g = **13.39 m/s2**, an illustrative H = **223 km** for an
H2/He atmosphere at 825 K (mean molecular weight 2.3), and about **191 ppm per
scale height**. At native sampling, the full-minus-no-CH4 transmission contour
midpoint spans about **347 ppm** within 3.05-3.65 microns, but this is not a retrieved
altitude or abundance.
Machine-readable outputs are in
[`figures/methane_consistency_statistics.csv`](figures/methane_consistency_statistics.csv)
and [`figures/methane_bin_contributions.csv`](figures/methane_bin_contributions.csv).
The complete 60-row design grid is in
[`results/methane_morphology_multiverse.csv`](results/methane_morphology_multiverse.csv),
with a compact [`result_summary.json`](results/result_summary.json).
## Research upgrade evidence
The 50→94 score is an expert repository-practice rubric, not peer review,
scientific merit, citation impact, or a literal multiplier of truth. Review the
[`baseline audit`](docs/BASELINE_AUDIT.md), [`methods`](docs/METHODS.md),
[`claims ledger`](docs/CLAIMS.md), [`limitations`](docs/LIMITATIONS.md), and
[`reproducibility guide`](docs/REPRODUCIBILITY.md).
## System context
- Radius: 11.20 Earth radii
- Mass: 170.99 Earth masses
- Orbital period: 3.067852 days
- Transit duration: 2.131 hours
- Semi-major axis: 0.0344 AU
- Equilibrium temperature: 825 K
- Host: WASP-80 · distance 49.79 pc
- Discovery: 2012 by Transit (SuperWASP)
## Limitations
- The orbit is assumed circular and the quadratic limb-darkening coefficients are fixed representative values; they are not atmosphere-grid interpolations.
- The scaled semi-major axis is derived from the saved composite semi-major axis and stellar radius; their uncertainties are not propagated.
- Midpoint freedom corrects accumulated ephemeris error but introduces a bounded timing search. ΔBIC, not a naïve one-parameter p-value, is used as the support gate.
- PDCSAP processing, dilution, stellar variability, transit-timing variations, and long-timescale covariance can still bias the inferred geometry.
- Radius ratio, impact parameter, and fixed limb darkening are correlated. Published global fits with physical priors and simultaneous detrending remain authoritative.
## Repository structure
```text
README.md
index.html
requirements.txt
configs/ frozen morphology-audit design
data/ unmodified TESS FITS + NASA row + source receipts
scripts/analyze_transit.py timing-adjusted limb-darkened transit fit
scripts/prepare_spectral_data.py verified 113-channel source reconstruction
scripts/analyze_methane_consistency.py source-data spectral robustness diagnostics
results/ complete machine-readable morphology audit
research/ maturity rubric and accessible comparison graph
figures/ generated plots and numerical summaries
docs/ methods, claims, limitations, and replay contract
tests/ real-data regression tests
.github/workflows/tests.yml CI on every push and pull request
LICENSE MIT
```
## References
1. [Triaud et al. 2013](https://ui.adsabs.harvard.edu/abs/2013A%26A...551A..80T/abstract) — discovery reference as listed by the NASA Exoplanet Archive.
2. Ricker, G. R. et al. (2015), *Transiting Exoplanet Survey Satellite (TESS)*, JATIS 1, 014003, [doi:10.1117/1.JATIS.1.1.014003](https://doi.org/10.1117/1.JATIS.1.1.014003).
3. TESS Team, *TESS Light Curves — All Sectors*, MAST, [doi:10.17909/t9-nmc8-f686](https://doi.org/10.17909/t9-nmc8-f686); Sector 54 used here.
4. [NASA Exoplanet Archive](https://exoplanetarchive.ipac.caltech.edu/), `pscomppars` TAP row retrieved 2026-08-15.
5. Bell, T. J. et al. (2023), *Methane throughout the atmosphere of the warm exoplanet WASP-80b*, Nature 623, 709-712, [doi:10.1038/s41586-023-06687-0](https://doi.org/10.1038/s41586-023-06687-0).
## Author
Biswajit Jana — [Portfolio](https://biswajit1999.github.io/Biswajit_Jana.github.io/) · [GitHub](https://github.com/Biswajit1999) · [LinkedIn](https://www.linkedin.com/in/biswajit-jana-27011a151/) · [ORCID](https://orcid.org/0009-0002-2411-1891)