I design and build all sorts of hardware relating to air-breathing (jet) propulsion, including gears. I agree with mkl. Those are not gear teeth. They have flat flanks, and no involute profile. No one makes gears with a gigantic U shaped root. They appear to me to most likely be clearance slots, to go around protruding bolt heads on a mating part. I have designed similar counterbore features myself.
What makes you claim that this part is steel? The article does not say that. Is that a fact, or are you guessing?
https://aviation.stackexchange.com/questions/90974/what-are-...
The exhausts that turn iridescent purple for a while due to heat are titanium, for example this 787. So I would suspect the debris is not titanium based on lack of heat marking.
https://www.reddit.com/r/aviation/comments/b77f5x/b787_its_s...
So if I were to guess what kind of metal it was solely based on coloration and suspected use case, I’d say Inconel.
But I wouldn’t make a guess at all, because it’s naive to assume that you can identify a type of metal based on a grainy freeze-frame of a cell phone video that has been re-encoded an unknown number of times before publication.
It seems surprising it weighs 500kg though, as it's held up by a thin iron/steel pipe/bar. If it's solid mild steel at 7850kg/m^3, with an outer radius of 1.2m and inner radius of 1.05m, and a thickness of 4cm, that would be (π*1.2^2 - π*1.05^2)*.04*7850 ≈ 333kg. If the inner radius is 1.0m and thickness is 5cm, that would be ~543kg, so maybe it is that heavy.
Edit: The tooth profile looks strange for a gear. There's a clear but potato-resolution view at 36s in the video. The teeth have flat tops with sharp corners, the sides are pretty vertical, and the gaps have very rounded bottoms.
[1] https://nation.africa/kenya/counties/makueni/mystery-object-...
How fast would you have to spin a gear ring to say, launch it on a ballistic trajectory and have it go supersonic? Maybe a factory somewhere had a _really_ catastrophic accident?
Then you tell people to relax when they dare question you. How about you relax, man?
But it turns out it might be from an Ariane upper stage after all.
But "ok...."
https://old.reddit.com/r/nextfuckinglevel/comments/1bmpxaq/t...
The diameter seems to match.
But maybe it really is Space Junk! https://www.youtube.com/watch?v=Z2dcVIEQwEE ("and now my Sally's dead...")
Proper scientific inquiry demands both an open mind and skepticism. That's why I didn't claim "it's definitely a cement mixer ring bearing" with the usual certainty of people arguing on the internet, but attempted to convey the unreliability of my source.