Can a Spherical Object in Space Achieve Fusion Without External Forces?

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Discussion Overview

The discussion centers around the conditions under which a perfectly spherical, stationary object in space could achieve nuclear fusion without external gravitational forces. Participants explore the mass thresholds required for fusion, the implications of these thresholds, and the outcomes for such an object.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants propose that a mass around 10% of the Sun's mass could achieve fusion, referencing external sources for additional information.
  • Others challenge this claim by questioning the absence of fusion signs from Jupiter, which is significantly less massive than the proposed threshold.
  • A participant recalls that the limit for hydrogen to helium fusion might be around 50 times the mass of Jupiter, suggesting that brown dwarfs, which are slightly more massive than Jupiter, could achieve fusion.
  • Another viewpoint suggests that while deuterium and tritium exist in other celestial bodies, a collapsing mass could ignite D-D fusion without reaching the conditions for proton-proton fusion.
  • One participant notes that Jupiter emits more energy than it receives from the Sun, speculating that this energy might not be due to fusion but rather from gravitational potential energy conversion.

Areas of Agreement / Disagreement

Participants express differing views on the mass required for fusion, with no consensus reached on the specific thresholds or the mechanisms involved. The discussion remains unresolved regarding the conditions under which fusion could occur in a spherical object in space.

Contextual Notes

Participants reference various mass thresholds and fusion processes, but the discussion lacks definitive conclusions and relies on speculative claims and external sources for support.

barycenter
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At what mass (if any) could a perfectly spherical, stationary object, without the influence of external gravitational forces, achieve fusion in space? Why/why not? What would, or would not, be the outcome of the sphere? Please supply link(s) to additional information.
 
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barycenter said:
At what mass (if any) could a perfectly spherical, stationary object, without the influence of external gravitational forces, achieve fusion in space? Why/why not? What would, or would not, be the outcome of the sphere? Please supply link(s) to additional information.

Yes, it's possible, limit is around 10% of mass of Sun. Additional information :
http://en.wikipedia.org/wiki/Star
 
xlines, thanks for replying. I do have a follow up question though. If you believe a mass about 1/10th the size of the Sun can achieve fusion, than why aren't there any signs of fusion coming from Jupiter?

As for the link to Wikipedia, I'm not too sure about their credibility, but I will check to see if their references hold water. I look forward to your follow-up answer.
 
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I think I recall that the limit for H-He fusion is about 50 times Jupiter masses (or something of that oderer of magnitude.)

And brown dwarfs are just 10 times more massive than jupiter.
 
Remember that deuterium, and to a lesser extent tritium, also exist in other planets and stars. A collapsing mass of matter could be massive enough to ignite D-D fusion but NOT P-P fusion. I think I read somewhere that Jupiter itself MIGHT have a small amount of fusion reactions going on thanks to this. (But take it with a grain of salt, as I have no idea where I heard that from)
 
barycenter said:
xlines, thanks for replying. I do have a follow up question though. If you believe a mass about 1/10th the size of the Sun can achieve fusion, than why aren't there any signs of fusion coming from Jupiter?.

Well, having only one in thousand mass of Sun, Jupiter is below stated limit. As far as I recall, Jupiter emits much more energy that it receives from Sun, but I can't claim it is fusion in origin. I recall vaguely that it has something with converting gravitational potential energy of helium droplets falling to heat or something ...
 

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