I How Does Technetium-99 Appear in Red Giants Beyond the Iron Peak?

[jjson775]

TL;DR Summary

Technetium 99 was detected in a red giant in 1952. Was this produced by nuclear fusion?

Technetium 99 was detected by spectroscopy in a red giant. How did it get there if it is heavier than the “iron peak”, the upper limit for fusion?

 

[mfb]

Iron/nickel is the limit where fusion releases energy. Fusion processes continue beyond that, they just don't release energy any more but need energy input.

https://en.wikipedia.org/wiki/R-process
https://en.wikipedia.org/wiki/S-process

 

[Vanadium 50]

To add, this is called the s-process, where heavy elements in the star absorb neutrons.

 

[jjson775]

Iron/nickel is the limit where fusion releases energy. Fusion processes continue beyond that, they just don't release energy any more but need energy input.

https://en.wikipedia.org/wiki/R-process
https://en.wikipedia.org/wiki/S-process

My question arose from a straightforward problem showing how the technetium could not have been present in the star from the beginning, because of radioactive decay. To test my understanding, the technetium was formed in the star by the endoergic s-process. Elements up to the iron peak can be created by ordinary fusion. Probably an oversimplification on my part.