My guess would be the remains of previous supernovas. I was rather intrigued by the similarity of many of the finds to stuff found in Lunar regolith (then I had a 'Well, duh!' moment).

I think this could be the kind of mission that would intrigue the public. At least comets and asteroids are something space that they're interested in. Honestly, I think that even with all of our troubles, if NASA proposed a couple of asteroid-looking instruments the public would have no trouble getting behind them. Something like L-1&2 point sentries looking at the stuff in towards the Sun and out into space. NASA, I'm sure, would muck it all up with politics and scientific squabbling.

Hmmm, maybe someone would be interested in -buying- that data...