4 ms·

"Sometimes called an 'artificial sun' for the sheer heat and power it produces" No, it's because the sun is also a fusion reactor.

Razengan 7y ago
Very dumb but honest question: How are we certain that stars are fusion reactors and not, say, the other ends of black holes?
- moh_maya 7y ago
  I am not an astrophysicist (or a physicist even) but one piece of evidence that may be useful here: Based on our understanding of the nuclear fusion reactions, starting from hydrogen, we expect to see, for a star of a given light / radiation spectrum (viz. Young stars, old, white dwarfs, super giants, etc ), emit spectra lines indicative of different elements such as H, He, O, C, etc. [1]. Young stars may not have all the "heavier elements", older stars do. Their relative abundance also changes with age. Our models & predictions of stellar nuclear fusion (afaik) correspond very well with the specific emission spectra we detect for different star types. Which also corresponds very well to the size / lifetime of star, etc. So, the data is very very consistent with nuclear fusion happening in stars. Now, it may be possible that they are just the "other ends" of white holes. But if it were so, then the model becomes far mode complex, plus, where are all the black holes? While I do not know if the total number / mass of all extant blackholes is as much as the total stellar mass, I would suspect it's far far lesser. Probably wouldn't add up. This is just the first explanation that came to my mind. I am certain there are others. Again, this is a non-physicist's lay analysis. Take it FWIW. :) [1] https://en.m.wikipedia.org/wiki/Astronomical_spectroscopy https://en.m.wikipedia.org/wiki/Astronomical_spectroscopy
  - deleted 7y ago
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- m3kw9 7y ago
  You could also ask if fusion is just energy from other ends of black holes. My point is that scientists can’t be there so see it but they have a very high probability that this is what is powering it based on theories and calculations
- pfdietz 7y ago
  There is good evidence on the internal structure of the Sun from helioseismology. The results confirm models of the Sun's structure and temperature to high precision. https://en.wikipedia.org/wiki/Helioseismology https://en.wikipedia.org/wiki/Helioseismology Because of this data, it was concluded that astrophysical explanations for the Solar Neutrino Problem (which cast doubt on fusion as the Sun's energy source) were not workable, and eventually a particle physics explanation (neutrino oscillations and the MSW effect) was shown to be the solution. The neutrinos are direct evidence that fusion is the Sun's energy source. https://en.wikipedia.org/wiki/Solar_neutrino_problem https://en.wikipedia.org/wiki/Solar_neutrino_problem

Razengan 7y ago

Very dumb but honest question: How are we certain that stars are fusion reactors and not, say, the other ends of black holes?

moh_maya 7y ago
I am not an astrophysicist (or a physicist even) but one piece of evidence that may be useful here: Based on our understanding of the nuclear fusion reactions, starting from hydrogen, we expect to see, for a star of a given light / radiation spectrum (viz. Young stars, old, white dwarfs, super giants, etc ), emit spectra lines indicative of different elements such as H, He, O, C, etc. [1]. Young stars may not have all the "heavier elements", older stars do. Their relative abundance also changes with age. Our models & predictions of stellar nuclear fusion (afaik) correspond very well with the specific emission spectra we detect for different star types. Which also corresponds very well to the size / lifetime of star, etc. So, the data is very very consistent with nuclear fusion happening in stars. Now, it may be possible that they are just the "other ends" of white holes. But if it were so, then the model becomes far mode complex, plus, where are all the black holes? While I do not know if the total number / mass of all extant blackholes is as much as the total stellar mass, I would suspect it's far far lesser. Probably wouldn't add up. This is just the first explanation that came to my mind. I am certain there are others. Again, this is a non-physicist's lay analysis. Take it FWIW. :) [1] https://en.m.wikipedia.org/wiki/Astronomical_spectroscopy https://en.m.wikipedia.org/wiki/Astronomical_spectroscopy
- deleted 7y ago
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m3kw9 7y ago
You could also ask if fusion is just energy from other ends of black holes. My point is that scientists can’t be there so see it but they have a very high probability that this is what is powering it based on theories and calculations
pfdietz 7y ago
There is good evidence on the internal structure of the Sun from helioseismology. The results confirm models of the Sun's structure and temperature to high precision. https://en.wikipedia.org/wiki/Helioseismology https://en.wikipedia.org/wiki/Helioseismology Because of this data, it was concluded that astrophysical explanations for the Solar Neutrino Problem (which cast doubt on fusion as the Sun's energy source) were not workable, and eventually a particle physics explanation (neutrino oscillations and the MSW effect) was shown to be the solution. The neutrinos are direct evidence that fusion is the Sun's energy source. https://en.wikipedia.org/wiki/Solar_neutrino_problem https://en.wikipedia.org/wiki/Solar_neutrino_problem