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Author Topic: Do All Neutron Stars Become Black Holes ?  (Read 4646 times)

Offline neilep

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Do All Neutron Stars Become Black Holes ?
« on: 23/02/2012 12:30:21 »
Wocha,

Neutron stars are like..well dense yes ?...They are even more dense than wifeys custard and that is very dense !

Look , here's one I drew whilst stopped at the traffic lights on my way to work.



A Neutron Star That I Just Drew (I did not photograph it as it's illegal to drive and use camera/phone here in UK but setting up my easel, brushes and paints was fine)

Nice eh ? being delivered next Tuesday as a toy for my cat to play with.


Now then, as mentioned Neutron stars are so dense that a little bit of one really weighs rather a lot so I imagine they have well strong gravity and stuff. As you know space isn't empty...it's like well plenum innit ?

so...my questions are...during the life of a Neutron star as it collects more stuff do they all become black holes ?...and so...How close is a Neutron start to becoming a black hole ?



whajafink ?


hugs and shmishes


mwah mwah


Neil
Did Ewe See The New Tron Film ?..It's Ok !
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Offline imatfaal

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Re: Do All Neutron Stars Become Black Holes ?
« Reply #1 on: 23/02/2012 13:41:17 »
Neutron stars are quite a way from becoming blackholes.  If a star (very roughly) has a mass 8ish times that of our sun it is likely to end as a neutron star - it will blow off its outer layers (more or less explosively) and the core will fall in on itself till atoms cannot remain as atoms and you get neutron degeneracy.   You will end up with a neutron star of between 1.4 to 3 solar masses.   Over 20-30 solar masses the explosion and shedding of the outer layers results in a black hole.

If you could add enough mass to a 3 solar mass neutron star you would end up passing the Tolmar-Oppenheimer-Volkoff limit and you would start getting really weird stuff.  Even then it is unlikely to be a black hole - but some other form of degenerate matter.

 The question is how you would get enough matter into the neutron star to change its mass that much.  Remember the neutron star is sitting right where a really massive star exploded - quite a lot of the locally available matter will have been attracted and eaten by the star and blown off in the explosion.

Even if there is a star neighbour of the neutron star willing to give up its matter to increase the neutron stars mass - there is another fly in the ointment: angular momentum.  Angular momentum will stop the matter flowing straight into the neutron star - and the neutron star is so small, that any in falling material ends up on a very shallow spiral into the star (it's basically a slow decay orbit).  The material in this spinning accretion disc moves at huge speed and generates huge heat through friction.  The huge rotating magnetic field of the neutron star may also mean that the very inside bit of the accretion disk is flung away from the star at the poles.

Basically, whilst a huge amount of material might be around the neutron star - the mass of the star itself will not be increased enough to change its nature
 

Offline neilep

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Re: Do All Neutron Stars Become Black Holes ?
« Reply #2 on: 23/02/2012 14:48:50 »
Neutron stars are quite a way from becoming blackholes.  If a star (very roughly) has a mass 8ish times that of our sun it is likely to end as a neutron star - it will blow off its outer layers (more or less explosively) and the core will fall in on itself till atoms cannot remain as atoms and you get neutron degeneracy.   You will end up with a neutron star of between 1.4 to 3 solar masses.   Over 20-30 solar masses the explosion and shedding of the outer layers results in a black hole.

If you could add enough mass to a 3 solar mass neutron star you would end up passing the Tolmar-Oppenheimer-Volkoff limit and you would start getting really weird stuff.  Even then it is unlikely to be a black hole - but some other form of degenerate matter.

 The question is how you would get enough matter into the neutron star to change its mass that much.  Remember the neutron star is sitting right where a really massive star exploded - quite a lot of the locally available matter will have been attracted and eaten by the star and blown off in the explosion.

Even if there is a star neighbour of the neutron star willing to give up its matter to increase the neutron stars mass - there is another fly in the ointment: angular momentum.  Angular momentum will stop the matter flowing straight into the neutron star - and the neutron star is so small, that any in falling material ends up on a very shallow spiral into the star (it's basically a slow decay orbit).  The material in this spinning accretion disc moves at huge speed and generates huge heat through friction.  The huge rotating magnetic field of the neutron star may also mean that the very inside bit of the accretion disk is flung away from the star at the poles.

Basically, whilst a huge amount of material might be around the neutron star - the mass of the star itself will not be increased enough to change its nature

WOW !!..Thanks Imatfaal !

Gosh !...you made me read stuff !....

Very much appreciate your concise response !...So, a Neutron star has a long way to go if it's to become a black hole.....I like the idea of a Quark star then a Preon star

I thought that seeing as ' space' is filled with lots of other stuff that even though the Neutron is where a large star used to be that it still would take on additional spacey ' flotsum and jetsum '  Admittedely this would take a long time....perhaps a few weeks yes ?  ;)...maybe a month !  ;)

Thanks again
 

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Re: Do All Neutron Stars Become Black Holes ?
« Reply #2 on: 23/02/2012 14:48:50 »

 

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