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K2-18 b
A temperate sub-Neptune studied through atmospheric spectroscopy.
- classification
- Sub-Neptune exoplanet
- system
- K2-18
K2-18 b is larger than Earth and unlike any Solar System planet. Tentative 2023-2025 JWST hints of dimethyl sulfide (DMS), a potential biosignature gas, remain low-confidence and contested by independent reanalyses; this is a disputed, tentative claim, not a confirmed detection, and atmospheric interpretations more broadly remain model-dependent and actively debated.
- Class
- Sub-Neptune exoplanet
- Location / system
- K2-18
- Distance
- About 120 light-years from Earth
Only values with an established scientific consensus are listed. Where a quantity is uncertain or model-dependent, it is discussed in the sections below rather than stated as data.
Overview (starter entry, expanded review pending)
K2-18 b is larger than Earth and unlike any Solar System planet. Tentative 2023-2025 JWST hints of dimethyl sulfide (DMS), a potential biosignature gas, remain low-confidence and contested by independent reanalyses; this is a disputed, tentative claim, not a confirmed detection, and atmospheric interpretations more broadly remain model-dependent and actively debated.
Transit photometry and spectroscopy
K2-18 b is not resolved as a surface. Its listed properties come from changes in host-star light or motion; atmospheric claims, where attempted, depend on instrument sensitivity and retrieval models.
- What remains least constrained about K2-18 b?Composition, internal structure, formation history or local environment can require different observations and may remain model-dependent.
Items above are unresolved. Hypotheses are labelled as such and are not presented as confirmed findings.
NASA/IPAC // verified 28 September 2026