A Neutron Star- inside a Red Giant?

[Aethon]

Astronomers have discovered the 'best' candidate so far for a Thorn- Zytkow object.

http://www.space.com/27389-hybrid-star-discovery-thorne-zytkow-object.html

[rtxoff]

I am not quite sure what makes this the best candidate for an Thorn-Zytkow object.

[Aethon]

If you know of another one with a similar spectrum I'd be interested to hear about it.

[Tommygun]

When a red giant swallows a much denser neutron star does the neutron star go straight to the core or does it orbit inside the red giant?

[sgt_flyer]

Well, i don't know their relative masses, but even then - the star's gases should slow their relative orbits through drag - so each should fall towards the barycenter. (Afterwards - does the star's cores merge or do they stay stuck next to each other, that's another story )

[magnemoe]

Well, i don't know their relative masses, but even then - the star's gases should slow their relative orbits through drag - so each should fall towards the barycenter. (Afterwards - does the star's cores merge or do they stay stuck next to each other, that's another story )

Yes drag will slow it down however an neutron star is very dense and heavy while the red giant is almost vacuum.

One interesting effect as it getting deeper where its real pressure it that the fusion should increase and as the report says it enables weird fusion because of the intense pressure

[lajoswinkler]

When a red giant swallows a much denser neutron star does the neutron star go straight to the core or does it orbit inside the red giant?

There's a reason why is the neutron star in the red giant in the first place. The giant inflated and the midget companion found itself trapped inside. They both orbit a mutual barycenter so we can say both of them will eventually slow down and come closer to the center. It should go at an exponential rate just like any other reentry, which is exactly what's happening, but on an awesome scale.

Such objects are probably relatively ephemeral. A neutron star with a giant stepping on its ass is rather close to collapsing into a black hole. The insides of the neutron star are basically neutrons, so the only related fusion activity is in its atmosphere which is the bottom of a red giant.

Even more interesting - the core of a Thorne-Żytkow object could be even more degenerate. Maybe there's a quark star inside of it, who knows?

[YNM]

There's a reason why is the neutron star in the red giant in the first place. The giant inflated and the midget companion found itself trapped inside. They both orbit a mutual barycenter so we can say both of them will eventually slow down and come closer to the center. It should go at an exponential rate just like any other reentry, which is exactly what's happening, but on an awesome scale.

Such objects are probably relatively ephemeral. A neutron star with a giant stepping on its ass is rather close to collapsing into a black hole. The insides of the neutron star are basically neutrons, so the only related fusion activity is in its atmosphere which is the bottom of a red giant.

Does this signifies that the envelope of RSGs are extremely puffy ? I mean, if TZO exist for a fair amount of time (so the neutron star only receives small drag), it can be used to calculate the small density of RSG envelope right ?

[lajoswinkler]

Does this signifies that the envelope of RSGs are extremely puffy ? I mean, if TZO exist for a fair amount of time (so the neutron star only receives small drag), it can be used to calculate the small density of RSG envelope right ?

It sounds plausible, yes, but TZOs as presented are objects in which the neutron star has already nested inside the giant star. I honestly have no idea if someone did simulations of the neutron star path inside the envelope to see how long it would last. I'm not even sure can we distinguish the nested from still "reentrying" TZOs based on spectrum. I doubt anyone has the slightest clue what exactly happens on the border.

It seems to me the only way we could know if the neutron star has nested is based on observing the Doppler shift because the reentrying type would wobble around barycenter.

But who knows how long does reentry last? If it's years, chances are extremely slim we'll ever recognize such object.

[-Velocity-]

Since I guess this kind of object won't work with a black hole, that means that the surface of the neutron star is critical in this kind of object. I guess at the core there must be a hell of a lot of fusion taking place on and near the surface of the neutron star itself, and that keeps the gas from just piling on and pushing it over the edge into a black hole. The outer surface of a neutron star is not actually neutrons, traditionally, it's supposed to be iron, but in THIS case, I guess it would be building up other elements too.

So how do these objects fuse elements heavier than iron? Remember, fusing elements heavier than iron is an endothermic reaction- fusing elements heavier than iron actually ABSORBS energy. Is it that the fusion of elements LIGHTER than iron is occurring so furiously near the core that supernova nucleosynthesis is taking place?! So it's sorta like a sustained supernova explosion?!?!

[lajoswinkler]

A black hole could survive inside a giant star. Of course, such object shouldn't last longer than TZO.

[-Velocity-]

A black hole could survive inside a giant star. Of course, such object shouldn't last longer than TZO.

Well, of course the black hole will survive...

I thought that when the core of a hypergiant collapses into a black hole, the result is thought to be a "long" duration GRB (on the order of a few minutes at most, I think) and maybe a hypernova. So the star wouldn't last long at all. But that's with like 50+ solar masses as an envelope, and this is with only maybe 10 solar masses. Supposedly though, these objects are also supposed to die in some kind of supernova explosion when the neutron star collapses into a black hole. I wouldn't exactly call the star "surviving" if it's in the process of destroying itself in a supernova explosion.

[lajoswinkler]

Well, of course the black hole will survive...

I thought that when the core of a hypergiant collapses into a black hole, the result is thought to be a "long" duration GRB (on the order of a few minutes at most, I think) and maybe a hypernova. So the star wouldn't last long at all. But that's with like 50+ solar masses as an envelope, and this is with only maybe 10 solar masses. Supposedly though, these objects are also supposed to die in some kind of supernova explosion when the neutron star collapses into a black hole. I wouldn't exactly call the star "surviving" if it's in the process of destroying itself in a supernova explosion.

I meant the system with the giant enveloping the hole, lol.

No, it would last a lot longer than minutes. If the star was collapsing at the speed of light, it would take hours for large red giants, but it's not. Those stars are so huge that any visible change requires a much longer time. Imagine stars the size of Jupiter orbit. Typical red supergiants. There are even larger ones. How long would the collapse last? The outer layers would probably never even move. The inner layers would do the work and push the outer ones away, but even they are enormous and don't move near the speed of light.

The same goes for supernovas. For some stupid reason, popular science has raised generations of people thinking it looks like fireworks or atomic bomb. It's a process that lasts for hours and days, in some cases probably even longer if pulsing occurs, what probably happens to Eta Carinae as we speak.

The star exists because of an equilibrium between gravitational contraction and radiation pressure. There isn't a reason why in certain cases a black hole couldn't exist in the center for a significant amount of time without the star collapsing. It's like trying to push a fatass through a pinhole. Even worse, actually.

There's plenty of fusion going around in the layers around the hole so that the radiation pressure can resist the weight of the material above.

In fact, black holes are in some cases possible to form in very large stars before the collapse and supernova (which lasts for a while - it's not "bang!") occurs.

Edited October 10, 2014 by lajoswinkler

[YNM]

So how do these objects fuse elements heavier than iron? Remember, fusing elements heavier than iron is an endothermic reaction- fusing elements heavier than iron actually ABSORBS energy. Is it that the fusion of elements LIGHTER than iron is occurring so furiously near the core that supernova nucleosynthesis is taking place?! So it's sorta like a sustained supernova explosion?!?!

They only mentioned enhanced ratios for Li versus Ca and K, Mo and Rb versus Fe and Ni. It doesn't really mean that it's happening sustainably, but the paper doesn't include the spectral graph of the star so I can't conclude.

[-Velocity-]

....

Yes, I know all that. I said it was the gamma ray burst that lasts a matter of minutes, not the supernova explosion.

My point is if the star is in the process of blowing itself apart, it is not "surviving", so the star does not survive for any significant amount of time with a black hole in its center, because, supposedly, black hole formation instantly triggers the beginning of a supernova explosion (a rapid inward gravitational collapse at the core). The explosion lasts months- but the gamma ray burst- if the long duration ones are really created by a black hole's jet firing within the innards of a star- is over in seconds or minutes.

I know what you mean about popular science and science fiction showing explosions in space happening at ludicrous speeds though. Just a few months ago, I laughed out loud while watching that new Superman movie with friends, when Krypton exploded at the speed of light. They didn't understand what was so funny.

The one that annoys me most is how popular science depictions of the Big Bang always show it happening at a single point and then spreading out into blackness. Grrrr....

Edited October 10, 2014 by |Velocity|

[magnemoe]

Yes, I know all that. I said it was the gamma ray burst that lasts a matter of minutes, not the supernova explosion.

My point is if the star is in the process of blowing itself apart, it is not "surviving", so the star does not survive for any significant amount of time with a black hole in its center, because, supposedly, black hole formation instantly triggers the beginning of a supernova explosion (a rapid inward gravitational collapse at the core). The explosion lasts months- but the gamma ray burst- if the long duration ones are really created by a black hole's jet firing within the innards of a star- is over in seconds or minutes.

I know what you mean about popular science and science fiction showing explosions in space happening at ludicrous speeds though. Just a few months ago, I laughed out loud while watching that new Superman movie with friends, when Krypton exploded at the speed of light. They didn't understand what was so funny.

The one that annoys me most is how popular science depictions of the Big Bang always show it happening at a single point and then spreading out into blackness. Grrrr....

Yes an large explosion last some time, this is also true for an nuclear explosion even if all power was released in microseconds. Its also hard to qualify then the explosion end.

Anyway, an neutron star inside an gas giant would give interesting fusion close to the neuron star as it gains an dense enough atmosphere.

Not only the hydrogen but also the stuff on the surface of the neutron star.

Yes they have an layer of normal matter over degenerated before reaching the neutron core.