Pythagoras, Pythagorean, Euclidean, Gravitational Lensing, Symmetry.
pictures may not represent the best achieved and reported measurement, but anyhow they are close to it. Adding the 3 values: α + β + γ = (39°± 1°) + (80°± 1°) + (91°± 1°) = 210°± 3°, which is 30° over the 180° expected in a triangle draw on a flat surface. Observe how the uncertainty propagation