Midinfrared imaging of alpha Orionis

We have imaged the M2Iab supergiant star alpha Ori at 11.7 and 17.9 mu m us ing the Hale 5 m telescope and an array camera with subarcsecond angular re solution. Our images reveal the circumstellar dust shell extending out to s imilar to 5 " from the star. By fitting two multiparameter models to the da ta, we find values for the dust shell inner radius, the temperature at this radius, the percentage flux produced by the circumstellar material at each of our wavelengths, and the radial dependence of the dust mass density. We present profiles of the mean surface brightness as a function of radius an d the power detected from within annular rings as a function of radius.