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We present a 0.5"-resolution diffraction-limited 17.7 micron image of the redsupergiant Antares obtained with the VLT mid-infrared instrument VISIR. TheVISIR image shows six clumpy dust clouds located at 0.8"--1.8" (43--96 stellarradii = 136--306 AU) away from the star. We also detected compact emissionwithin a radius of 0.5" from the star. Comparison of our VISIR image taken in2010 and the 20.8 micron image taken in 1998 with the Keck telescope revealsthe outward motions of four dust clumps. The proper motions of these dustclumps amount to 0.2"--0.6" in 12 years. This translates into expansionvelocities (projected onto the plane of the sky) of 13--40 km/s with anuncertainty of +/-7 km/s. The velocities of the dust clumps cannot be explainedby a simple accelerating outflow, implying the possible random nature of thedust cloud ejection mechanism. The inner compact emission seen in the 2010VISIR image is presumably newly formed dust, because it is not detected in theimage taken in 1998. The mass of the dust clouds is estimated to be(3-6)x10^{-9} Msun. These values are lower by a factor of 3--7 than the amountof dust ejected in one year estimated from the (gas+dust) mass-loss rate of2x10^{-6} Msun/yr, suggesting that the continuous mass loss is superimposed onthe clumpy dust cloud ejection.

Imaging the outward motions of clumpy dust clouds around the red supergiant Antares with VLT/VISIR