Imagine a rogue planet drifting in intergalactic space. For the sake of specificity, suppose that it is the size of Jupiter and composed of pure hydrogen. What will happen to it over the next $10^{200}$ years?

  • Will the planet slowly disintegrate via Jeans escape (possibly assisted by stray X-rays/gamma rays)?
  • Will the hydrogen atoms fuse together? If so, would fusion proceed via muon catalysis or quantum tunneling?
  • Will the planet accrete enough hydrogen from gas clouds to turn into a star?
  • Will the planet collide with another large object (for example, a star or black hole)?
  • Will the protons decay via sphalerons?

All of these are extremely slow processes, and I don't have much of an intuition for which ones proceed relatively fastest.


I'm primarily interested in currently known physical processes. Unless you really think it's important, I would prefer not to speculate too much about GUT's or quantum gravity.

Yes, I understand that all matter will eventually turn into photons over an infinite time scale (via sphalerons or, if necessary, micro black holes and Hawking radiation – we don't need to assume proton decay). However, I'm interested in what happens before then.

  • $\begingroup$ this probably cannot be answered . It is all about midels.. see svs.gsfc.nasa.gov/11541 . One would have to model something like that in intergalactic spaces. My guess would be, if formed it would keep on going as a rogue planet.if it is not caught by a system. and become a pure gas comet, (if it exists in the first place) $\endgroup$ – anna v Mar 13 '19 at 6:39

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