Direct Extragalactic Distance Determination Using X-Ray Scattering
  We examine the feasibility of using dust-scattered X-rays for direct determination of distances to nearby galaxies with bright background AGNs, QSOs, or GRBs. We show how the Chandra X-Ray Observatory could be used to determine the distance to M31 to an unprecedented absolute accuracy of 1%. 
B.T. Draine and Nicholas A. Bond (Princeton University Observatory)