Defining Habitability
Scientists assess exoplanet habitability by examining a combination of stellar, planetary, and environmental factors. While the classic “habitable zone” (or “Goldilocks zone”) is a starting point, recent research highlights many additional criteria.
Key Factors
Stellar Type
Stable, long-lived stars (K‑ and G‑type) provide steady energy over billions of years, giving life a chance to develop.
Orbital Distance
The planet must receive enough stellar flux to keep liquid water on its surface without boiling away.
Planetary Mass
Masses between ~0.5–5 Earth masses maintain a stable atmosphere and support plate tectonics.
Atmospheric Composition
A substantial atmosphere with greenhouse gases regulates temperature and protects against radiation.
Magnetic Field
Deflects stellar wind, preserving the atmosphere and shielding the surface from harmful particles.
Orbital Eccentricity
Low eccentricity ensures a stable climate; high eccentricity can cause extreme temperature swings.