The presence of which element would indicate that a star is going through a high mass star life cycle as opposed to loe mass star life cycle

Iron.

Explanation:

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In this case, when the star's core starts being composed mostly of iron, the undergoing nuclear reactions can no longer continue into the star. It turns out that the star start running out  of fuel, therefore it begins a temperature decrease as long as iron's melting temperature is larger.  In such a way, the  star flares up and consequently its inner temperature raises so the large heat causes the gases to  burst until it swells up and subsequently turns into a glowing red giant larger than the original  star.

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they it depends on if one believes about radioactivity, they make a geiger counter beep but maybe it was going to beep anyway electronics do wierd things all the time or it was programmed to beep near certain metals.