The Sun

Assembled from 30 blocks · 3 evidence · 27 related

1. Story
2. A G-type main-sequence star roughly 4.6 billion years old, currently a little under halfway through its core hydrogen supply. Its central temperature is about 15.7 million K and essentially all of its output comes from the proton-proton chain. It is the only star whose interior can be probed directly: helioseismology reads its internal structure from surface oscillations, and neutrino detectors measure the fusion reactions themselves in real time, including the CNO cycle first detected in solar neutrinos by Borexino in 2020. Its future is a model result rather than an observation. Core hydrogen exhaustion is generally placed around five billion years from now, and the detailed evolutionary calculation of Schroeder and Connon Smith (2008) puts the tip of the red giant branch at 7.59 billion years from now, with the Sun shedding about 0.332 solar masses and the Earth failing to escape engulfment despite the orbital expansion that mass loss produces. Not a place on Earth.
3. Knowledge
4. Main sequence (core hydrogen burning)
5. Hydrogen fusion: the proton-proton chain and the CNO cycle
6. The Sun
7. Connections
8. Hydrogen fusion: the proton-proton chain and the CNO cycle
9. Main sequence (core hydrogen burning)
10. The Sun forms and settles onto the main sequence
11. Payne concludes that stars are mostly hydrogen - and disclaims it
12. Neutrinos from the solar CNO cycle are detected
13. Initial stellar mass
14. Main sequence (core hydrogen burning)
15. Stellar nucleosynthesis
16. The Sun
17. Payne concludes that stars are mostly hydrogen - and disclaims it
18. Neutrinos from the solar CNO cycle are detected
19. Initial stellar mass
20. Protostar
21. Red giant and asymptotic giant branch
22. Hydrogen fusion: the proton-proton chain and the CNO cycle
23. The Sun
24. Hertzsprung-Russell diagram
25. The Sun forms and settles onto the main sequence
26. Hertzsprung and Russell independently plot luminosity against temperature
27. Evidence
28. Models the Sun to the tip of the red giant branch at 7.59 Gyr from now with 0.332 solar masses lost, and concludes the Earth is engulfed despite orbital expansion. Journal, volume, pages and DOI come from publisher and ADS listings via search; the paper was not fetched, so the model assumptions behind the engulfment result are not independently characterised here.
29. Reports the first direct detection of solar neutrinos from the CNO cycle. Title and DOI were read from the publisher listing via search; the paper was not fetched, and the quoted ~1 per cent CNO share of solar energy output comes from accompanying institutional summaries rather than the paper.
30. Supports general stellar-physics statements in this pack: mass-luminosity scaling, main-sequence lifetimes, degeneracy support and the conventional 1.4 solar mass Chandrasekhar value. This is university-maintained educational reference material, not primary literature, and it was read via search summary rather than fetched. Primary citations should replace it for any figure a reader might quote.