> This is an effort to characterize the zodiacal light, the solar system's illuminated dust, along with the galactic background and any light in darkest areas, by a massive reprocessing of raw data from Hubble, which is just underway.

Was my first guess, random small stuff like dust, ice, possibly some gas molecules reflecting light as they orbit/hang out around the solar system. I do wonder how much of an improvement we'd have visually if we could somehow drag JWST or something like it beyond that dust/debris cloud into the bare, emptier space.