Historical development of exoplanet discoveries.

Abstract

Since the discovery of the first exoplanets outside our Solar System in 1992 and 1995, the field of exoplanet research has rapidly expanded. Exoplanets, orbiting stars, differ from dwarf planets in mass and ability to clear their protoplanetary disks. The International Astronomical Union defined exoplanets in 2001, setting criteria for their classification. Historical references to exoplanets date back to Epicurus and Giordano Bruno, while Isaac Newton speculated on their existence. Early observations in the 19th century suggested the presence of exoplanets, but definitive detections proved elusive until the 1990s. The discovery of exoplanets around a pulsar in 1992 and a main sequence star in 1995 marked significant milestones. Subsequent discoveries, including "hot Jupiters" and multiple-planet systems, expanded our understanding. NASA's Kepler Satellite launch 2009 accelerated exoplanet discoveries, revealing more minor planets, some potentially habitable. Notably, Kepler-16 became the first extrasolar planet found in a binary system. As of February 8, 2024, the Extrasolar Planet Database Encyclopedia lists 5618 confirmed exoplanets, demonstrating the remarkable growth in our knowledge of these distant worlds.