In movies when there's a huge explosion in space, there's always this ring that comes out from the explosion. No!
In space the blast wave would be spherical: it only looks like a 2d ring when observed from a telescope many many light years away, since the telescope can only pick up the outside edge of the blast.
I remember very vividly when they redid the special effects in the original Star Wars trilogy and added this dumbass ring coming out of the Death Star explosion. It completely broke immersion for me because I was like “wtf is that supposed to be?”
You could make an argument that there was some kind of huge spinning gyroscope reaction wheel system on that axis which projected the explosion that way.
My thought is that it's revealing the construction and weak points of the death star. It may have been constructed in two hemispheres that were joined together, and that seam might have been the failure point where gassed were released when the internal pressure got too high.
Except then we should see the two hemispheres blow out from each other a bit, which they don't.
Hell, in Star Trek VI, where the Praxis Effect originates, it's a horrifying industrial accident that blows up Praxis, so for all we know there might well have been some kind of moon-sized particle accelerator that blew up and did cause that ring shape. But it seems to show up in a lot of places where there's not as justifiable an excuse.