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Detection of the Intrinsic Size of Sagittarius A* through Closure Amplitude Imaging (includes Online Supporting Material)

Geoffrey C. Bower·Heino Falcke·Robeson M. Herrnstein·Jun-Hui Zhao·W. M. Goss·Donald C. Backer
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Abstract

We have detected the intrinsic size of Sagittarius A*, the Galactic Center radio source associated with a supermassive black hole, showing that the short-wavelength radio emission arises from very near the event horizon of the black hole. Radio observations with the Very Long Baseline Array show that the source has a size of $24 \pm 2$ Schwarzschild radii at 7 mm wavelength. In one of eight 7-mm epochs we also detect an increase in the intrinsic size of $60^{+25}_{-17}$%. These observations place a lower limit to the mass density of Sgr A* of $1.4\times10^{4}$ solar masses per cubic astronomical unit.

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Geoffrey C. Bower, Heino Falcke, Robeson M. Herrnstein, Jun-Hui Zhao, W. M. Goss, Donald C. Backer. 2004-03-31. Detection of the Intrinsic Size of Sagittarius A* through Closure Amplitude Imaging (includes Online Supporting Material). https://doi.org/10.1126/science.1094023

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