# What is the end-state for a neutron star? **URL:** \ **Category:** Factual Questions\ **Created:** [September 16, 2021, 6:15am UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736 "2021-09-16T06:15:44Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [September 16, 2021, 6:15am UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736/1 "2021-09-16T06:15:44Z")
We know our sun will eventually end up as a white dwarf star and, in time, it will become a black dwarf (a long, long, long time…so long none exist yet in our universe). But what about neutron stars? I have never seen anything that suggests what happens to them in the far distant future. Particularly, we see some neutron stars eject jets of matter from their poles (i.e. pulsars). Surely there is an endgame to that. As massive as they are they can’t spout matter forever. So, what happens to them (eventually)? ---
**Author:** ![Johnny\_Bravo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_bravo/32/493_2.png) [@Johnny\_Bravo](https://boards.straightdope.com/u/Johnny_Bravo)\ **Post date:** [September 16, 2021, 10:58am UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736/2 "2021-09-16T10:58:25Z")
They cool down. The ones spouting energy are relatively young. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [September 16, 2021, 11:14am UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736/3 "2021-09-16T11:14:19Z")
Yeah, but that isn’t an eventual state. One would expect a spinning neutron star to eventually stop, and for most of the internal processes to cease coupling energy to the outside world (probably mostly as a result of it no longer spinning.) But what happens _eventually_? It will still radiate energy as a black body, which means it will reach eventually equilibrium with the CMB, which is likely to be shifted to something silly as the universe ages. But one wonders what the end game is. Does electron capture eventually render it a pure mass of neutrons? Is there an intermediate state where quantum uncertainty/tunnelling leaves it as a sort of psuedo-ground state of different sorts of matter in shells? Neutron stars can absorb matter or combine with other neutron stars and become black holes, but one assumes that isn’t expected to be the long term fate of every one of them. ---
**Author:** ![Jasmine](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jasmine/32/2964_2.png) [@Jasmine](https://boards.straightdope.com/u/Jasmine)\ **Post date:** [September 16, 2021, 11:51am UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736/4 "2021-09-16T11:51:29Z")
> [@Francis\_Vaughan](#): > > Yeah, but that isn’t an eventual state. One would expect a spinning neutron star to eventually stop, and for most of the internal processes to cease coupling energy to the outside world (probably mostly as a result of it no longer spinning.) But what happens _eventually_ ? A neutron star is a stable entity. The gravitational field is so immense that the electrons of the atoms are squeezed into their nuclei to form an incredibly dense sphere that is, in effect, a giant nucleus in and of itself. Virtually nothing can penetrate it much less break it apart. Being a solid neutron core of immense density, there is no internal instability at all. Unless it is swallowed up by a wandering Black Hole, it isn’t going to change at all. It will continue to spin because the void of space is a vacuum, and there is no friction to stop the spinning. It’s magnetic field will remain steady as it spins at a rate that may be 600 times a second. If it’s magnetic poles are disassociated from its rotational axis, it will be the kind of neutron star known as a pulsar. As the old song goes, “That’s all there is.” ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [September 16, 2021, 1:19pm UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736/5 "2021-09-16T13:19:55Z")
> [@Jasmine](#): > > It will continue to spin because the void of space is a vacuum, and there is no friction to stop the spinning. But space isn’t 100% empty. There’s meteors, dust, gasses, and gravitational interactions. Earth’s rotation has slowed down by a half hour in the last 70 million years, and six hours since 1.4 billion years ago. That’s almost entirely due to the moon’s gravitational forces, but even without the moon, on an infinite time scale those little things matter. ---
**Author:** ![Ike\_Witt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ike_witt/32/283_2.png) [@Ike\_Witt](https://boards.straightdope.com/u/Ike_Witt)\ **Post date:** [September 16, 2021, 1:41pm UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736/6 "2021-09-16T13:41:54Z")
A chance to recommend one of my favourite YouTube channels - PBS Space Time just put out a video yesterday called [Neutron Stars: The Most Extreme Objects in the Universe](https://www.youtube.com/watch?v=1Ou1MckZHTA). There are several more videos about neutron stars on the channel as well. Anton Petrov also has great videos about neutron stars and magnetars and FRBs. ---
**Author:** ![Horatius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/horatius/32/3572_2.png) [@Horatius](https://boards.straightdope.com/u/Horatius)\ **Post date:** [September 16, 2021, 1:46pm UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736/7 "2021-09-16T13:46:36Z")
> [@Jasmine](#): > > It will continue to spin because the void of space is a vacuum, and there is no friction to stop the spinning. The spin rate tends to decrease over time: > **[Neutron star | Spin down](https://en.wikipedia.org/wiki/Neutron_star#Spin_down)** > > Over time, neutron stars slow, as their rotating magnetic fields in effect radiate energy associated with the rotation; older neutron stars may take several seconds for each revolution. This is called spin down. The rate at which a neutron star slows its rotation is usually constant and very small. > The periodic time (P) is the rotational period, the time for one rotation of a neutron star. The spin-down rate, the rate of slowing of rotation, is then given the symbol > > > > > ... ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [September 16, 2021, 2:10pm UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736/8 "2021-09-16T14:10:26Z")
I know that protons are thought to eventually decay (with a half life \> 10^{30} years). I expect neutrons will too. I would expect that the same Hawking radiation that allows black holes to disintegrate would also affect neutron stars. ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [September 16, 2021, 2:19pm UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736/9 "2021-09-16T14:19:53Z")
Kurzgesagt has a video on neutron stars too but I can’t recall if they talk about their ultimate fate. They’re usually very good about that sort of thing, I just can’t re-watch it right now. [![](https://img.youtube.com/vi/udFxKZRyQt4/maxresdefault.jpg "Neutron Stars – The Most Extreme Things that are not Black Holes") ](https://www.youtube.com/watch?v=udFxKZRyQt4) ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [September 16, 2021, 2:38pm UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736/10 "2021-09-16T14:38:12Z")
> [@Jasmine](#): > > If it’s magnetic poles are disassociated from its rotational axis, it will be the kind of neutron star known as a pulsar. But how long can it spout matter out of the poles as a pulsar? As dense as a pulsar is the amount of matter is finite. How does a pulsar switch off? Can a neutron star get rid of enough matter to un-neutron star itself and become a white dwarf? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 17, 2021, 12:18am UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736/11 "2021-09-17T00:18:36Z")
Pulsars (mostly) don’t spew matter. They mostly just spew light. There probably is some incidental matter that gets caught up in that, but as they cool and the radiation decreases, and matter-splash would also decrease. And even at its peak, it’s not much. A neutron star in a binary or other multiple star system might end up with matter accreting onto it from its partner(s), and that can lead to dramatic results like surface fusion or even collapse into a black hole. But isolated neutron stars wouldn’t have any source of accretion worth mentioning. ---
**Author:** ![Ruken](https://avatars.discourse-cdn.com/v4/letter/r/f475e1/32.png) [@Ruken](https://boards.straightdope.com/u/Ruken)\ **Post date:** [September 17, 2021, 11:10am UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736/12 "2021-09-17T11:10:51Z")
> [@Hari\_Seldon](#): > > I would expect that the same Hawking radiation that allows black holes to disintegrate would also affect neutron stars. I was trying to find whether neutron stars “evaporate” like black holes and encountered some randos on other message boards saying that Hawking radiation require an event horizon. So I’m not sure. They certainly cool. Primarily with neutrinos until much later, when photons dominate. But I haven’t seen anything on what happens if you cool off a neutron star that was barely big enough to become one in the first place. ---
**Author:** ![tavaritz](https://avatars.discourse-cdn.com/v4/letter/t/71e660/32.png) [@tavaritz](https://boards.straightdope.com/u/tavaritz)\ **Post date:** [September 17, 2021, 11:57am UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736/13 "2021-09-17T11:57:05Z")
My understanding of the Universe is that it eventually comprises only of black holes that then will radiate away by Hawking radiation slowly until the end of entropy. This implies that all neutron stars will end by being consumed by black holes. ---
**Author:** ![Steve\_MB](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/steve_mb/32/5339_2.png) [@Steve\_MB](https://boards.straightdope.com/u/Steve_MB)\ **Post date:** [September 17, 2021, 1:12pm UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736/14 "2021-09-17T13:12:43Z")
Over a really long timescale, any given neutron star will gain mass (either by impacts of other objects or accretion from the surrounding not-quite-vacuum) until it becomes massive enough to collapse into a black hole. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [September 17, 2021, 8:39pm UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736/15 "2021-09-17T20:39:44Z")
> [@Ruken](#): > > I was trying to find whether neutron stars “evaporate” like black holes and encountered some randos on other message boards saying that Hawking radiation require an event horizon. So I’m not sure. IANAP, but according to Stephen Hawking’s own conceptual explanation of the nature of what is now called Hawking radiation, yes, it absolutely requires the event horizon of a black hole. As I recall from what was even originally only a simplified explanatory concept in Hawking’s Cambridge Lectures, it has to do with quantum fluctuations in a vacuum which can be thought of as creating virtual particle anti-particle pairs with net zero energy that almost immediately annihilate each other. Since one of the paradoxical properties of an event horizon is that any particle that passes beyond it is cut off forever from all interactions with the universe, if the black hole absorbs one of the virtual particles it allows the other one to become a real particle with positive energy and potentially escape into space as a real particle, perhaps a photon. This stream of real particles is Hawking radiation, and since the black hole has gained negative energy, by energy-mass equivalence it loses a tiny bit of mass. No doubt there are far more accurate characterizations of this phenomenon. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [October 7, 2021, 1:15am UTC](https://boards.straightdope.com/t/what-is-the-end-state-for-a-neutron-star/950736/16 "2021-10-07T01:15:16Z")
> [@Chronos](#): > > Pulsars (mostly) don’t spew matter. They mostly just spew light. I just re-watched this video which suggests a pulsar is spewing particles (queued to the proper time in the video): [![](https://img.youtube.com/vi/1Ou1MckZHTA/maxresdefault.jpg "Neutron Stars: The Most Extreme Objects in the Universe") ](https://www.youtube.com/watch?v=1Ou1MckZHTA&t=135)