How many exoplanets might be habitable in our galaxy?

The answer

As of 2025, over 6,000 exoplanets have been confirmed, with NASA's TESS mission and ground-based surveys adding roughly 200 per year. Statistical analysis of Kepler mission data suggests that approximately 20-25% of Sun-like stars host a rocky planet in the habitable zone - the orbital distance where liquid water could exist on the surface. With roughly 200 billion stars in the Milky Way, this implies 10-40 billion potentially habitable rocky planets. JWST has begun analyzing exoplanet atmospheres through transmission spectroscopy, detecting water vapor, carbon dioxide, and methane in gas giant atmospheres. The TRAPPIST-1 system, with seven rocky Earth-sized planets (three in the habitable zone), remains a prime target. However, habitability depends on many factors beyond distance: magnetic fields, atmospheric composition, stellar activity, and tidal locking all influence whether a planet could support life.