Gravitational redshift of the Sun

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Science  18 Dec 2020:
Vol. 370, Issue 6523, pp. 1429-1430
DOI: 10.1126/science.370.6523.1429-e

General relativity predicts that light emitted from a massive body is redshifted by its gravitational field. This gravitational redshift effect has previously been verified using white dwarfs and terrestrial experiments. Measuring it for the Sun is complicated by the motions of plasma on the surface, which Doppler-shift spectral lines by amounts similar to that of the predicted signal. González Hernández et al. analyzed a high-resolution spectrum of sunlight reflected off the Moon, thereby averaging over the solar disc, calibrated using a laser frequency comb. After compensating for plasma motions, they measured a gravitational redshift that is consistent with general relativity, within the uncertainty of 1 to 2%.

Astron. Astrophys. 643, A146 (2020).

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