Bradley Discovers Aberration of Starlight

English astronomer James Bradley announced his discovery of the aberration of starlight to the Royal Society in January 1729. Through observations of the star Gamma Draconis between 1725-1728, he detected an annual shift in the star's apparent position that could not be explained by parallax. Bradley determined this phenomenon resulted from the combined effect of Earth's orbital motion and the finite speed of light. This discovery provided the first direct observational evidence for the heliocentric model, confirming that Earth revolves around the Sun. Bradley calculated the speed of light to within approximately 2% of its correct value.