It is immediately apparent from IRAS and other far infrared data (figure 1) that all known FU Orionis stars, or fuors, are associated with substantial amounts of cool circumstellar dust.

The pre-outburst magnitudes for V1057 Cyg indicate that this star was immersed in circumstellar dust already before its flare-up in 1969–1970, and hence that this dust did not - as has been claimed - appear only after the outburst; regrettably there exist no far infrared data from that time. The colours also exclude the possibility that the star then was of the alleged spectral type KO, but point to it being of a rather early type and obscured by both interstellar, local, and circumstellar matter. For details, see Welin 1985.