326 | Natalie Batalha on What We Know and Will Learn About Exoplanets

What It Covers

Natalie Batalha explains how the Kepler and TESS missions discovered thousands of exoplanets through transit photometry, what we've learned about planetary populations, and how JWST studies exoplanet atmospheres to search for habitability.

Key Questions Answered

• •Exoplanet abundance: Kepler data reveals every star in the Milky Way has at least one planet on average, with the nearest potentially habitable planet located approximately 10 light years away, suggesting billions of planets exist throughout our galaxy alone.
• •Super-Earth dominance: The most common planet type orbiting within one astronomical unit are super-Earths or mini-Neptunes, ranging from 1.5 to 2 times Earth's radius. These planets don't exist in our solar system, yet dominate the galaxy's planetary population.
• •Atmospheric detection challenge: Rocky planets orbiting M dwarf stars, which comprise 70 percent of galactic stars, may lack atmospheres due to intense stellar radiation during formation. JWST observations over the next five years will determine if these planets retain atmospheres.
• •Transit spectroscopy method: JWST observes planetary transits at a thousand colors simultaneously, measuring how atmospheric molecules like carbon dioxide absorb specific wavelengths. This reveals chemical compositions by detecting deeper light dips at absorption wavelengths, achieving part-per-million precision.
• •Mass-radius relationship: Combining transit photometry for radius measurements with Doppler spectroscopy for mass measurements yields planetary density. This bulk density distinguishes gas giants at one gram per cubic centimeter from rocky planets at five grams per cubic centimeter, revealing composition.