10.4 Exoplanet Atmospheres
Over 5,000 exoplanets discovered. Transit and emission spectroscopy reveal atmospheric composition. JWST is revolutionizing this field.
Detection Methods
Transit Spectroscopy
Light filtering through atmosphere during transit reveals absorption features (H₂O, CO₂, CH₄, Na, K).
Emission Spectroscopy
Thermal emission from day side (secondary eclipse) reveals temperature structure.
Notable Discoveries
Hot Jupiters
Tidally locked, 1000+ K. Water vapor, carbon monoxide detected.
TRAPPIST-1 System
7 Earth-sized planets. Rocky, potentially habitable. JWST studying atmospheres.
K2-18b
Potential "Hycean" world. Water vapor detected. Possible biosignature hints.
Biosignatures
Looking for O₂, O₃, CH₄ together as signs of life.
Habitability
The habitable zone is where liquid water can exist. But atmospheric composition, magnetic fields, and stellar activity all matter for true habitability.