Astronomical evidence
WASP-39 b is a hot, low-density giant orbiting a Sun-like star every 4.055 days. During transit, its extended atmosphere imprints absorption features on the starlight that passes through it. The resulting spectrum contains information about chemistry at the planetary limb. A feature near 4.05 micrometers was attributed to sulfur dioxide. Tsai and colleagues showed how ultraviolet light can drive reactions that produce this molecule from sulfur-bearing precursors. The abundance inferred from the observations calls for photochemistry beyond a simple chemical-equilibrium picture. This is a concrete way in which a planet is connected to its star: photons alter atmospheric chemistry as well as supplying heat. The result concerns a hot giant’s atmosphere. Sulfur dioxide in this context is not evidence of biology, an ocean or an inhabited surface.
The illustrated viewpoint
Colonial chain of living vesicles in a still, inward-folded meditative pose. An invented orbital habitat; the hot atmosphere is outside. The crescent, cloud bands and orbital chamber are illustrative. Their colors and spatial detail are not resolved by the transmission spectrum, and the habitat is a fictional place from which to view the planetary limb.
The crescent, cloud bands and orbital chamber are illustrative. Their colors and spatial detail are not resolved by the transmission spectrum, and the habitat is a fictional place from which to view the planetary limb. All depicted life is fictional. The visual connection to the cosmos is an artistic theme, not a claimed biological mechanism.
Catalog measurements & sources
Host: WASP-39. Snapshot: 25 September 2026. Errors, limits and source provenance are retained. Calculated values and model estimates are not direct measurements. Unknown is not zero; equilibrium temperature is not surface temperature.
| Quantity / unit | Value / reported errors | Source |
|---|---|---|
| Radius · Earth radii | 14.3363 (+0.44836 / -0.44836) | Mancini et al. 2018 |
| Mass · Earth masses | 89.3102 (+10.1706 / -10.1706) | Mancini et al. 2018 |
| Density · g/cm³ | 0.167 (+0.023 / -0.023) | Mancini et al. 2018 |
| Orbital period · days | 4.05529 (+3.4e-06 / -3.4e-06) | Mancini et al. 2018 |
| Orbital semimajor axis · AU | 0.04828 (+0.00082 / -0.00082) | Mancini et al. 2018 |
| Eccentricity | 0 | Carter et al. 2024 |
| Inclination · degrees | 87.32 (+0.17 / -0.17) | Mancini et al. 2018 |
| Irradiation · Earth flux | 316.269 | ExoFOP |
| Equilibrium temperature · K | 1166 (+14 / -14) | Mancini et al. 2018 |
| Stellar effective temperature · K | 5485 (+50 / -50) | Mancini et al. 2018 |
| Stellar radius · Solar | 0.939 (+0.022 / -0.022) | Mancini et al. 2018 |
| Stellar mass · Solar | 0.913 (+0.047 / -0.047) | Mancini et al. 2018 |
| Stellar luminosity · log Solar | -0.12792 (+0.0194 / -0.01286) | Panek et al. 2023 |
| Stellar age · Gyr | 8.5 (+4 / -3.4) | Mancini et al. 2018 |
| Stellar metallicity · dex | 0.01 (+0.09 / -0.09) | Mancini et al. 2018 |
| Distance · pc | 213.982 (+1.76 / -1.731) | TICv8 |