Probably nickel and/or salts of barium. Copper burns blue as a pyrotechnic colorant.

A lot of spaceship debris looks like this because copper is used in a lot of rocket engines.

Alternatively or additionally, I think oxygen plasma glows blue or green, because northern lights (near the poles, at least) are greenish.

They’re not necessarily accidental (for example, taking long exposures during a meteor shower), but yes the vast majority of meteor pictures are by chance. A few meteors have been detected just before entry and photographed but that number is in the single digits.

Nah, we predict metoer showers all the time.

I don’t understand why they call it an “accident”. The camera was set up and taking timed pictures. I just don’t think “accident” is accurate

but still they come