Exoplanetology

Exoplanetology is the scientific study of planets outside the Solar System. It covers the detection, confirmation, and characterization of exoplanets, as well as the interpretation of their diversity in the context of planetary formation and evolution. The field draws on astronomy, planetary science, atmospheric science, and astrobiology to understand the physical properties, orbital configurations, and potential habitability of worlds beyond Earth.

Main observational methods include the transit method, radial velocity, direct imaging, microlensing, and timing variations. Transits reveal planetary radii and, together with mass measurements, densities; radial velocity provides mass and orbital parameters; direct imaging offers atmospheric spectra for young, widely separated planets; microlensing accesses distant systems. Space missions such as Kepler and K2, and later TESS, have produced large catalogs of planet candidates, enabling population-level analyses.

Key topics are planet demographics, formation and migration, atmospheric composition and climate, and potential habitability. The field studies how planets form in protoplanetary disks, how they migrate, and how their atmospheres evolve under stellar irradiation. Classifications typically separate rocky, Earth-sized planets from sub-Neptunes and gas giants, with attention to the radius gap and occurrence rates as functions of stellar type.

Historically, exoplanets were discovered in the 1990s around pulsars and, shortly after, around Sun-like stars. The Kepler mission transformed the field by identifying thousands of candidates; JWST and ground-based spectrographs are advancing atmospheric characterization. Ongoing and planned facilities, including PLATO and future extremely large telescopes, aim to improve mass, radius, and spectral measurements and to search for biosignatures in favorable environments.