In the 1919 Eddington eclipse experiment, what astronomical effect was measured near the Sun?

In the 1919 Eddington eclipse experiment, astronomers measured starlight deflection near the Sun.

During a total solar eclipse, Arthur Eddington’s expedition photographed stars that appeared close to the darkened Sun. Their apparent positions were compared with photographs of the same stars taken when the Sun was elsewhere in the sky.

The measured shift was interpreted as evidence that the Sun’s gravity bends light, as predicted by Albert Einstein’s general theory of relativity. The eclipse made the effect observable because the Moon blocked the Sun’s overwhelming brightness.

The observations were historically important, although the original measurements had large uncertainties and later analyses have debated how strong the evidence was. The modern prediction is firmly supported by many more precise observations, including gravitational lensing and radio measurements.