What elemental signature might specific blue signals sometimes be linked to, besides Magnesium, due to excitation under high-energy conditions?

Answer

Copper

Some astronomical observations link specific blue signals to the presence of Copper (Cu) or the excitation of atmospheric Nitrogen under very specific, high-energy conditions.

What elemental signature might specific blue signals sometimes be linked to, besides Magnesium, due to excitation under high-energy conditions?
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