Exoplanetssystem

An exoplanetssystem is a star and its gravitationally bound planetary companions, together with any moons or belts of debris that orbit it. Exoplanetssystem display a wide range of architectures: some host only a single planet, while others contain multiple planets in compact, coplanar orbits. They can include hot Jupiters close to the star, tightly packed multi-planet systems, and planets on highly eccentric orbits. The diversity informs models of planet formation and migration.

Formation and dynamics: Most systems are believed to form from a protoplanetary disk around a young star. Core accretion, disk-driven migration, and planet–planet gravitational interactions shape the final arrangement. Resonances, eccentricities, and inclinations arise from these processes, while debris disks and moons reflect later evolution. Systems vary in stability and long-term dynamics.

Detection and study: Exoplanets are detected by transit (dips in starlight), radial velocity (wobbles of the star), direct imaging, and gravitational microlensing. Large surveys such as Kepler, K2, and TESS have revealed thousands of planets and many multi-planet systems, enabling population statistics. Observational biases favor large, close-in planets, so discoveries still miss much of the true diversity.

Habitability and notable examples: The habitable zone is the region where liquid water could persist, and some systems host planets within or near that zone. Notable examples include TRAPPIST-1, Kepler-90, and Proxima Centauri, illustrating diverse architectures from resonant chains to nearby terrestrial candidates. Ongoing observations and future telescopes aim to determine compositions, atmospheres, and potential habitability.