I'm loosely following the Barnacles stories in both threads.
I had a few thoughts, and if they have been discussed before, just ignore this post

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Alien planetary extraction site: What if the picture shows an alien planetary extraction site, similar to the one humans are using. Difference is, since the AU looks organic and if linked, the extractors might be too and are organic hybrids. Thinking about it - Barnacle can also refer to a lichen
Link, a symbiotic organism that has more capabilities than the individual organism, these alien extractors harvest the resources from the planet and convert it into the meta material. So I expect to find a structure surrounded or next to the barnacles. This one is called British Soldiers, just showing lichen can make these structures.
Their bubble. I’d like to think that the AU’s are something like frontier markers of their habituated space. And that the location of the Barnacles is within their bubble, or as stated within the nebula. I posted a nebula theory earlier on along with a list of supernova – the closest one is Crab Nebula. Anyway, at this point I’ll look for metal rich / high metal content planets in their bubble, since I would expect them to have these harvesting outpost a bit farther away from the Seven Sisters.
I’m heading out with my combat/explorer ASP to their bubble. Wish me luck.
Cheers,
CMDR Ray Mobula