The Elite Dangerous forums are provided for discussions of the game.
The Astronomy Forum is in Off topic because it is not about the game.
While I understand the reasoning and know that forum structure decisions aren't easy to make, I believe that a little more leeway for scientific threads in here should be allowed.
1.) As others have said, the grey area between what is relevant to the game and what isn't is quite large. Threads like the one where Jackie Silver, Ziljan and others try to understand and explain the scientific principles behind the procedural generated galaxy are treasure chests of knowledge that require real world scientific knowledge to appreciate.
2.) The choice of off-topic topics is quite odd. Astronomy is a single topic that mostly concerns Elite players (Zoo Tycoon players don't get a dedicated 'animals' section

) yet it is as far awy from the Elite fora as possible. Which leads me to:
3.) I mostly use my phone to visit the fora (it shows in the grammar) and mobile browsers are not the most elegant way to navigate them. Information gets lost and overlooked more easily, my bookmark leads me directly to the Elite section so that I won't have to filter stuff I don't care about. My choice, I know, but something that is relevant these days.
I don't need a merge; but I'd really like a less strict policy on letting real-world astronomy/-physics threads remain here. As a whole, explorers are a mature bunch of reasonable people; and we wouldn't start flooding the forum with APOD threads. And a lot of science stuff isn't as off-topic to us as it would seem on the first glance.