Testing General Relativity with High-Resolution Imaging of Sgr A*
  Submilliarcsecond astrometry and imaging of the black hole Sgr A* at the Galactic Center may become possible in the near future at infrared and submillimetre wavelengths. This resolution is sufficient to observe the silhouette the supermassive black hole in the Galactic center casts upon background emission. However, more exciting is the prospect of observing ``hot spots'' in the accretion flow. Here we discuss how such measurements may be used to test not only the consistency of General Relativity, but also the validity of the Kerr metric in particular. 
Avery Broderick, Abraham Loeb (Harvard University)