haiguise

Looks like that might get reverted [0].

[0] https://github.com/numpy/numpy/pull/25955

Yes, see for example http://mesa.sourceforge.net/index.html which is a stellar evolution code used a lot in astrophysics.

The dark spot is the shadow and the faint circle is the moon.

Yup, the more massive a star the short it lives. The Sun for example will live around 10 billion years, whereas a star 10 times the mass of the Sun will only live for 30 or so million years.

Using some hand-wavy arguments you could say that fusion pauses a star's collapse, so the more massive a star is, the more energy generation it needs to stay in equilibrium during this pause.

CNO fusion does happen but at a fraction of the rate of pp fusion at the core temperature of the Sun. CNO fusion is more efficient in the sense that it is much more strongly temperature dependent. For pp fusion, the rate goes with T^4, but for CNO it is T^20.

See eg. https://websites.pmc.ucsc.edu/~glatz/astr_112/lectures/notes... for a more detailed explanation.

See for example MESA http://mesa.sourceforge.net/index.html an open source set of modules for software experiments in stellar astrophysics, which is still actively developed.