Eksoplaneet

Eksoplaneet are planets that orbit stars other than the Sun. They can also include planets that roam freely in interstellar space without being bound to a star. Since the early 1990s, thousands have been confirmed using a variety of detection methods, making exoplanet research one of the fastest-growing areas in astronomy.

Detection methods include the transit method, which detects small dips in a star’s brightness as a planet passes in front; the radial-velocity method, which measures Doppler shifts in starlight caused by an orbiting planet; direct imaging, which captures light from the planet itself; gravitational microlensing, which uses a foreground star’s gravity to magnify a background star; and astrometry, which tracks tiny changes in a star’s position. Space missions such as Kepler and TESS, along with ground-based instruments like HARPS, have driven most discoveries.

Exoplanets show remarkable diversity. They range from gas giants larger than Jupiter to rocky, Earth-sized worlds, and they orbit at distances from their stars that create hot, short-period planets as well as temperate worlds in or near the habitable zone. Many systems host multiple planets, and atmospheric studies—particularly of transiting planets—have revealed molecules such as water vapor and clouds in some atmospheres.

Discovery and significance: Exoplanet science began with planets around pulsars in the early 1990s and the first around a Sun-like star in 1995. The field informs models of planet formation, migration, and the potential for life beyond the Solar System.

Notable examples include Proxima Centauri b, the seven-planet TRAPPIST-1 system, the compact Kepler-90 system, and hot Jupiters like 51 Pegasi b, illustrating the broad range of exoplanets.