Research Article

# Detection of the Intrinsic Size of Sagittarius A* Through Closure Amplitude Imaging

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Science  30 Apr 2004:
Vol. 304, Issue 5671, pp. 704-708
DOI: 10.1126/science.1094023

## 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 ± 2 Schwarzschild radii at 7-millimeter wavelength. In one of eight 7-millimeter epochs, we also detected an increase in the intrinsic size of $Math$. These observations place a lower limit to the mass density of Sagittarius A* of 1.4 × 104 solar masses per cubic astronomical unit.

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