The equatorial ring of Supernova ( SN ) 1987A has been exposed to forward shocks from the SN blast wave , and it has been suggested that these forward shocks have been causing on-going destruction of dust in the ring .
We obtained SOFIA FORCAST 11.1 , 19.7 and 31.5 \mu m photometry of SN 1987A in 2016 .
Compared with Spitzer measurements 10 years earlier , the 31.5 \mu m flux has significantly increased .
The excess at 31.5 \mu m appears to be related to the Herschel 70 \mu m excess , which was detected 5 years earlier .
The dust mass needed to account for the the 31.5–70 \mu m excess is 3–7 \times 10 ^ { -4 } M _ { \odot } , more than ten times larger than the ring dust mass ( \sim 1 \times 10 ^ { -5 } M _ { \odot } ) estimate from the data 10-years earlier .
We argue that dust grains are re-formed or grown in the post-shock regions in the ring after forward shocks have destroyed pre-existing dust grains in the ring and released refractory elements into gas .
In the post-shock region , atoms can stick to surviving dust grains , and the dust mass may have increased ( grain growth ) , or dust grains might have condensed directly from the gas .
An alternative possibility is that the outer part of the expanding ejecta dust might have been heated by X-ray emission from the circumstellar ring .
The future development of this excess could reveal whether grains are reformed in the post-shocked region of the ring or eject dust is heated by X-ray .