Detection and Characterization of Exoplanets Using Transit Photometry

Transit photometry has established itself as one of the most powerful and versatile techniques in exoplanet science, driving the discovery of thousands of planets and enabling quantitative studies of their physical properties. Completeness-corrected analyses of Kepler photometry demonstrate that small exoplanets (≈1–4 R⊕) are common around FGKM stars across a wide range of orbital periods. Advances in detection methodology, including transit least-squares searches and machine-learning–based validation frameworks, have significantly improved sensitivity to shallow transits and reduced false-positive contamination. Beyond demographics, transit photometry has become central to atmospheric characterization through transmission spectroscopy with facilities such as the James Webb Space Telescope (JWST). This paper discusses the methodological foundations of transit photometry, including light-curve extraction, transit detection, modelling, and validation. Key scientific outcomes from major surveys, particularly Kepler and TESS, are highlighted, including planet occurrence rates, multi-planet system architectures, and the discovery of the planetary “radius valley,” which provides evidence for atmospheric mass-loss processes in small planets. The role of transit timing variations and joint analyses with radial-velocity data in constraining planetary masses and bulk compositions is also examined. Current limitations, notably stellar activity and observational biases, are critically assessed. Transit photometry will remain central to exoplanet discovery and atmospheric studies in the era of next-generation observatories.