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D3f4lt_player t1_jdir7xy wrote

Reply to comment by Aseyhe in Could a black hole just be a big neutron star that just has gravity so high light cant escape? by SlyusHwanus

do all neutron stars collapse into a black hole?

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KnoWanUKnow2 t1_jdixvdp wrote

No. Most don't. But a neutron star that continues to accumulate mass can. For example if 2 neutron stars collide they can form a black hole. We detected one of these mergers on August 17, 2017.

One that doesn't accumulate mass will, in theory, slowly lose mass until it explodes into a white dwarf in about 10^(38) years (if proton decay is real). Since the universe is much younger than that, this hasn't happened yet.

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D3f4lt_player t1_jdj101g wrote

how will it become a white dwarf during proton decay? isn't that the phase when all stars die?

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djublonskopf t1_jdjofch wrote

The idea is, if protons do indeed randomly decay (over extremely long periods of time), then a neutron star will very slowly lose mass via this process, with protons in its thin outer crust very occasionally evaporating. After about 10^(38) years, enough mass will have been lost that the neutron star finally reaches a tipping point where it is light enough to not be a neutron star anymore. So it explodes into a white dwarf.

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awawe t1_jdkgvaz wrote

>After about 10^(38) years,

Where does this figure come from, given that we don't yet know whether protons decay or not, let alone their half life?

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saxophysics t1_jdl559y wrote

There is a lower bound on the half-life, so I’m assuming this number is using that lower bound. The correct statement would then be after at least 10^38 years

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D3f4lt_player t1_jdjrgvw wrote

oh so it will take a long time for protons to decay and the universe go back to a soup of subatomic particles (this time the soup is cold). then the black holes take over because these abnormalities don't care about atomic structures, as long as it got mass or energy it's gonna be eaten

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mfb- t1_jdkg2fd wrote

They will take over only in the sense that they will still be around, there won't be matter left for them to capture - it will all be spread out too far at that time.

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kamill85 t1_jdlcc9f wrote

Wait, but Neutron Star, proton decay or not, losses mass anyway, every second, because all the emitted EM equals loss of mass/energy. I'm pretty sure it would lose a sizeable chunk by 10^38, or by the time it cools down (if ever)

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loki130 t1_jdltbsg wrote

That emission comes out of their heat and angular energy; they'll slow, cool, and dim long before that point.

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Kneenaw t1_jdiz9q7 wrote

Not all Neutron stars will expand to the mass/density required to collapse into Black Holes. These ones will exude visible light for about one billion years before cooling down below visible light, then live on for about 1e+38 years before decaying completely into a kind of neutron white dwarf which will then decay further for another 1e+38 years before becoming a neutron black dwarf which will be there to witness the elder years of the universe.

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