Exoplanetsplanets

Exoplanets, or extrasolar planets, are planets that orbit stars beyond the Sun. The term Exoplanetsplanets is not a standard designation in astronomy; it seems to be a repetition of the words exoplanets and planets and is not used in professional literature. If encountered, it should be interpreted as referring to exoplanets generally or as a typographical variant in data labeling.

Most exoplanets have been discovered using transit photometry and the radial velocity method. Transit surveys detect dips in starlight when a planet passes in front of its star; radial velocity detects the star's wobble due to gravitational tug. Other methods include direct imaging, microlensing, and astrometry.

Exoplanets vary greatly in size and composition: Earth-sized rocky worlds, ice giants, and gas giants. Orbits range from ultra-short periods to multi-year ones; many planets lie closer to their stars than Mercury does in our solar system. Some reside in the habitable zone where liquid water could exist, but habitability depends on atmosphere and other factors.

The first confirmed exoplanets were discovered in the early 1990s around pulsars and Sun-like stars. The Kepler mission, launched in 2009, identified thousands of planet candidates and enabled population studies. The Transiting Exoplanet Survey Satellite (TESS) has found nearby planets, while the James Webb Space Telescope and other facilities are enabling atmospheric characterization.

Exoplanet research has become a central part of planetary science, informing theories of planet formation and evolution, and guiding the search for potentially habitable worlds and biosignatures. The field continues to grow with new discoveries and increasingly detailed measurements of planetary properties.