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The equatorial ring of Supernova (SN) 1987A has been exposed to forwardshocks from the SN blast wave, and it has been suggested that these forwardshocks have been causing on-going destruction of dust in the ring. We obtainedSOFIA FORCAST 11.1, 19.7 and 31.5 micron photometry of SN\,1987A in 2016.Compared with Spitzer measurements 10 years earlier, the 31.5 micron flux hassignificantly increased. The excess at 31.5 micron appears to be related to theHerschel 70 micron excess, which was detected 5 years earlier. The dust massneeded to account for the the 31.5--70 micron excess is 3--7x10^-4 Msun, morethan ten times larger than the ring dust mass (1x10^-5 Msun) estimate from thedata 10-years earlier. We argue that dust grains are re-formed or grown in thepost-shock regions in the ring after forward shocks have destroyed pre-existingdust grains in the ring and released refractory elements into gas. In thepost-shock region, atoms can stick to surviving dust grains, and the dust massmay have increased (grain growth), or dust grains might have condensed directlyfrom the gas. An alternative possibility is that the outer part of theexpanding ejecta dust might have been heated by X-ray emission from thecircumstellar ring. The future development of this excess could reveal whethergrains are reformed in the post-shocked region of the ring or eject dust isheated by X-ray.

SOFIA mid-infrared observations of Supernova 1987A in 2016 --- forward shocks and possible dust re-formation in the post-shocked region?