Solar Gravitational Deflection of Radio Waves Measured by Very-Long-Baseline Interferometry

Abstract

Utilizing a four-antenna technique, we observed simultaneously, at each end of an 845-km baseline, the radio sources 3C279 and 3C273B which are 10° apart in the sky. Differences in interferometric phases at 3.7-cm wavelength monitored near the time of the 1972 occultation of 3C279 by the sun, yielded a gravitational deflection of 0.99±0.03 times the value predicted by general relativity, corresponding to $\gamma =0.98\mathrm{}\pm 0.06$ (standard error).