I understand that the 9 realms comes from Norse mythology. But with regards to the MCU why would the Asgardians even have a term for this when they clearly have ventured further out than just those 9 specific planets?
I can't remember where exactly, but I seem to remember Thor saying something to the effect of "if it existed in the 9 realms, Asgard would have known about it", as if the 9 realms were all that Thor would have had knowledge of, and he was surprised by any form of technology or even sentient life outside of the 9 realms.
After which I was caught off guard in Agents of Shield when Sif made a comment about the alien corpse possibly being Kree. And even more caught off guard at the end of Dark World when Sif and the Warriors Three went and visited the Collector.
Could this have possibly just been a continuity break between the team involved with the first Thor movie, and the rest of the MCU?