Redshifts Generated by Light Deflection in Gravitational Fields

Einstein’s general theory of relativity predicts that a difference in the gravitational potentials between two locations in a gravitational field would introduce a redshift or blueshift for a light ray travelling from one location to another. However, observations made in our solar system, such as the 21 cm radiation line from Taurus A near occultation by the Sun, the Pioneer-6 spacecraft experiments and the solar limb effect, clearly demonstrate that there exist anomalous redshifts which could not be explained by current theories and models. Here we show that besides the well-known Einstein gravitational redshift, which has been verified by various observations, there exists an extra gravitational redshift, which is caused by the change in a photon’s momentum produced in a curved spacetime. We demonstrate that this type of gravitational redshift is just the super-gravity redshift, as expected in the literature. We derive a mathematical expression for the super-gravity redshift by using a theoretical model: a photon moving in a static Schwarzschild geometry and then apply it to calculate the centre-to-limb redshift variations across the solar disc. It is found that the redshift distribution predicted by the theoretical model agrees well with one of the observed profiles of the solar spectrum lines around 6300 Å, which demonstrates that the extra gravitational redshift should be the mechanism behind the solar limb effect and other observed anomalous redshifts.