Mid-infrared images of the circumstellar dust around alpha Scorpii

We present the first two-dimensional mid-infrared images of the circumstell ar dust distribution around the supergiant star alpha Scorpii. Our observat ions were made at wavelengths of 12.5 and 20.8 mum using the MIRLIN focal-p lane array camera on the Keck II 10 m telescope, with spatial resolution (l ambda /D) of 0."29 and 0."48 at the two wavelengths, respectively. Our deco nvolved images, which provide a resolution enhancement of approximately a f actor of 2, show that the dust shell previously detected in one-dimensional scans is actually highly nonuniform. Specifically, the shell is now seen t o be concentrated largely into three discrete clumps, and there is evidence of a more recent ejection which has left a central concentration of dust w ithin about 0."3 from the star.