First Stellar Parallax Measurement

Friedrich Wilhelm Bessel published the first reliable measurement of stellar parallax in 1838, providing empirical evidence of Earth's orbit around the Sun. After 18 months of observations at Königsberg Observatory, Bessel detected an annual shift of 0.314 arcseconds in the star 61 Cygni, calculating its distance at approximately 10.3 light-years. This measurement addressed a major objection to heliocentrism that had persisted since Copernicus's time: the lack of observable stellar parallax. Bessel's work established the first reliable stellar distance measurement and demonstrated that stars are located at vast distances from the solar system.