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thritham
2011-Jul-05, 08:29 AM
Hi, I was recently reading information regarding deaths/destiny of stars (white dwarfs, black-holes, neutron stars, magnatars, etc....) and believe that, based on the mass and composition of star, it must be possible to predict ALL possible outcomes and that there must be a definitive table/list (akin to the periodic table). I would be especially interested to learn if there are some outcomes which can be physically predicted but have not yet been discovered.

Thritham

loglo
2011-Jul-05, 03:58 PM
Hi thritham
Yes, there is. It is called the Hertzsprung–Russell diagram (http://en.wikipedia.org/wiki/Hertzsprung%E2%80%93Russell_diagram). There is some more detail here:-
http://outreach.atnf.csiro.au/education/senior/astrophysics/stellarevolution_hrintro.html (http://outreach.atnf.csiro.au/education/senior/astrophysics/stellarevolution_hrintro.html)

As you would expect, like the periodic table is to chemistry, it is a powerful tool for organising information about stellar properties.

chornedsnorkack
2011-Jul-05, 04:09 PM
Hertzsprung-Russell diagram has no mass axis, nor time axis. Stars evolve on the Hertzsprung-Russell diagram.

There are parts which are not well predicted. Supernovae, for example, do not seem to be sufficiently well understood to predict with confidence which stars become neutron stars and which black holes.

Also there are outcomes which cannot have been observed because they cannot have happened. Such as fate of low mass stars.

thritham
2011-Jul-05, 05:50 PM
so is there a table which has mass, composition and time? A little like filling in the gaps between what we predict & observe and what can be predicted but not observed?

Romanus
2011-Jul-05, 10:24 PM
There are parts which are not well predicted. Supernovae, for example, do not seem to be sufficiently well understood to predict with confidence which stars become neutron stars and which black holes.

This. There is similar uncertainty in determining the boundary between a star that will leave only a white dwarf, and that which will go supernova and leave a neutron star, due to vigorous mass loss in the star's old age.

Nereid
2011-Jul-06, 12:20 AM
Hi, I was recently reading information regarding deaths/destiny of stars (white dwarfs, black-holes, neutron stars, magnatars, etc....) and believe that, based on the mass and composition of star, it must be possible to predict ALL possible outcomes and that there must be a definitive table/list (akin to the periodic table). I would be especially interested to learn if there are some outcomes which can be physically predicted but have not yet been discovered.

Thritham(bold added)

In addition to what's already been noted, there's another aspect, which follows from the fact that single, isolated stars are not all that common.

When a star is in a binary, its evolution may depend - critically, sometimes - on the fine details of the joint evolution.

For example, the more massive of the pair may evolve to red giant stage, and transfer mass to the other, because it (the more massive one) fills its Roche lobe (do you know what this is?). That - initially less massive - star may then have a fate very different from that of a star that started out with the same mass and composition, but was a singleton all its life.

Another example: in a case like the above, the second star later becomes a red giant, and feeds mass onto its now white dwarf partner; the partner thus undergoes several nova episodes, and finally becomes a Type 1a supernova ... or not.

And that's just two examples.

While the broad outlines of the joint evolution of close binaries is now more or less understood, the details - especially in terms of accurate prediction, given initial mass and composition - are not.

thritham
2011-Jul-06, 06:27 AM
Thanks for the replies. If we leave out the complications caused by binary systems, then I would like to imagine that, based on mass and compostion - as well as our understanding of particle physics - we can (computer) modell the outcomes for isolated stars?

Nereid
2011-Jul-06, 10:44 PM
Thanks for the replies. If we leave out the complications caused by binary systems, then I would like to imagine that, based on mass and compostion - as well as our understanding of particle physics - we can (computer) modell the outcomes for isolated stars?
The outcome for isolated stars is already pretty well understood:

- the lowest mass objects never became stars, and never will; they will slowly cool and one day become like frozen Jupiters

- brown dwarfs, which had brief lives as stars, will follow the same path

- low mass stars, below a certain limit, will be like brown dwarfs, but will take an extremely long time to stop being stars (trillions of years)

- somewhat more massive stars, like our Sun, will become red giants, blow off their outer envelopes, and end up as white dwarfs; white dwarfs will cool, and their non-degenerate atmospheres one day freeze

- more massive still, and a core collapse supernova is the fate, resulting in either a neutron star or a black hole; neutron stars will cool quite quickly, and their final state should be most interesting!

For a given star/object, its fate will depend primarily on its mass and then on its composition; the mass+composition which makes a star end up as a white dwarf vs a neutron star, for example, is only approximately known (mostly, as I understand it, to do with uncertainties over how much mass a star will lose before it turns off the main sequence, as well as while it's a giant/supergiant).

Interestingly, the only stars which will end up as nothing more than an expanding cloud of (hot) gas are those which are in binaries (or, very rarely, are involved in a collision with another star); as far as I know, Type 1a supernovae is not a fate of isolated stars!

Tensor
2011-Jul-07, 04:53 AM
The outcome for isolated stars is already pretty well understood:

snip...

For a given star/object, its fate will depend primarily on its mass and then on its composition; the mass+composition which makes a star end up as a white dwarf vs a neutron star, for example, is only approximately known (mostly, as I understand it, to do with uncertainties over how much mass a star will lose before it turns off the main sequence, as well as while it's a giant/supergiant).

The chart located here (http://books.google.com/books?id=GzlrW6kytdoC&pg=PA203&lpg=PA203&dq=masami+wakano&source=bl&ots=15Ocos1QzQ&sig=AZSFj2dgthQBFLRSbubXw-8vnVU&hl=en&ei=MygVTseRDJLqgQezvNAw&sa=X&oi=book_result&ct=result&resnum=8&ved=0CEAQ6AEwBw#v=onepage&q=masami%20wakano&f=false) scroll up a bit. (I tried to find the diagram somewhere else, but this book is the only place I've been able to find it). The diagram does not include the recent possibilities of "quark stars" (http://www.citebase.org/fulltext?format=application%2Fpdf&identifier=oai%3AarXiv.org%3Aastro-ph%2F0407155). This is mainly due to extreme uncertainty on the behavior of the color force at high densities.

There were two candidates for quark stars. One RX J1856.5-3754 was first thought to be one as it's temperature was thought to be 700,000, leading to a diameter of 4-8 km, too small for a neutron star. Later measurements fixed the temperature at ~400,000 meaning the diameter is ~14 km, right in line with neutron star theories. The other, 3C 58 has been showing excessive cooling, this is still considered a candidate.

Recently, another candidate had been considered (XTE J1739-285) due to it's high spin rate, (1122 hz that works out to 67,320 RPM). However, that observation has not been verified and it is no longer a candidate. Several supernovae (http://arxiv.org/pdf/0708.1787v4) have been considered as possible candidate quark stars (http://arxiv.org/abs/nucl-th/0610013). I want to emphasize that these are still pretty speculative, but there are possibilities.

chornedsnorkack
2011-Jul-08, 01:51 PM
The outcome for isolated stars is already pretty well understood:

- the lowest mass objects never became stars, and never will; they will slowly cool and one day become like frozen Jupiters

- brown dwarfs, which had brief lives as stars, will follow the same path

- low mass stars, below a certain limit, will be like brown dwarfs, but will take an extremely long time to stop being stars (trillions of years)

- somewhat more massive stars, like our Sun, will become red giants, blow off their outer envelopes, and end up as white dwarfs; white dwarfs will cool, and their non-degenerate atmospheres one day freeze
!
Not really. The long term fate of a low mass stars is different from that of either brown dwarfs or sunlike stars. Obviously it has never happened.


- more massive still, and a core collapse supernova is the fate, resulting in either a neutron star or a black hole; neutron stars will cool quite quickly, and their final state should be most interesting!

For a given star/object, its fate will depend primarily on its mass and then on its composition; the mass+composition which makes a star end up as a white dwarf vs a neutron star, for example, is only approximately known (mostly, as I understand it, to do with uncertainties over how much mass a star will lose before it turns off the main sequence, as well as while it's a giant/supergiant).

Interestingly, the only stars which will end up as nothing more than an expanding cloud of (hot) gas are those which are in binaries (or, very rarely, are involved in a collision with another star); as far as I know, Type 1a supernovae is not a fate of isolated stars!

How about pair instability supernovae?

Nereid
2011-Jul-08, 07:06 PM
Not really. The long term fate of a low mass stars is different from that of either brown dwarfs or sunlike stars. Obviously it has never happened.
And that (predicted, per theory) fate is ...?


How about pair instability supernovae?
Aren't they predicted to end as either neutron stars or black holes (or, possibly, quark stars)?

IIRC, they are a 'just' a different kind of core-collapse supernova, aren't they?

I perhaps should have added that singleton Pop III supergiants may have had fates somewhat different from those of particularly massive Pop I or Pop II main sequence supergiants (i.e. black hole-dom), if CDM (cold dark matter) does have a small, but non-zero, self-annihilation probability (or otherwise minimally self-interacts). This is, obviously, a highly speculative area ...

Nereid
2011-Jul-08, 07:10 PM
The chart located here (http://books.google.com/books?id=GzlrW6kytdoC&pg=PA203&lpg=PA203&dq=masami+wakano&source=bl&ots=15Ocos1QzQ&sig=AZSFj2dgthQBFLRSbubXw-8vnVU&hl=en&ei=MygVTseRDJLqgQezvNAw&sa=X&oi=book_result&ct=result&resnum=8&ved=0CEAQ6AEwBw#v=onepage&q=masami%20wakano&f=false) scroll up a bit. (I tried to find the diagram somewhere else, but this book is the only place I've been able to find it). The diagram does not include the recent possibilities of "quark stars" (http://www.citebase.org/fulltext?format=application%2Fpdf&identifier=oai%3AarXiv.org%3Aastro-ph%2F0407155). This is mainly due to extreme uncertainty on the behavior of the color force at high densities.

There were two candidates for quark stars. One RX J1856.5-3754 was first thought to be one as it's temperature was thought to be 700,000, leading to a diameter of 4-8 km, too small for a neutron star. Later measurements fixed the temperature at ~400,000 meaning the diameter is ~14 km, right in line with neutron star theories. The other, 3C 58 has been showing excessive cooling, this is still considered a candidate.

Recently, another candidate had been considered (XTE J1739-285) due to it's high spin rate, (1122 hz that works out to 67,320 RPM). However, that observation has not been verified and it is no longer a candidate. Several supernovae (http://arxiv.org/pdf/0708.1787v4) have been considered as possible candidate quark stars (http://arxiv.org/abs/nucl-th/0610013). I want to emphasize that these are still pretty speculative, but there are possibilities.
Thanks for this; I'd completely forgotten about quark stars!

How do they fit in answer to the OP's question? I don't know, but would guess that they are possible fates of stars within a small mass-composition space ...

chornedsnorkack
2011-Jul-08, 08:02 PM
And that (predicted, per theory) fate is ...?



The stars of approximately solar mass can be seen completing their evolution. Not following a single star, astronomers are not that old, but the universe is slightly older than the total lifetime of the Sun. The old stars of globular clusters, and spread around Milky Way as well, include stars of roughly solar mass (initially), so the red giants are the brightest stars of globular clusters (and a nearby one is Arcturus).

Solar mass stars first fuse protium in their centre (main sequence) then protium around the centre (red giant branch) then helium in the centre (while continuing to fuse protium around - in horizontal branch) and finally helium around the centre (asymptotic giant branch). By that point they have shed most of their hydrogen envelope and do not fuse the remaining carbon core.

Brown dwarfs cannot sustain protium fusion and cool down into a cold body that, unlike a white dwarf, consists of protium rather than carbon.

Now, low mass stars sustain slow protium fusion. But when protium is exhausted, what is needed to start helium 4 fusion by triple alpha process?


Aren't they predicted to end as either neutron stars or black holes (or, possibly, quark stars)?

IIRC, they are a 'just' a different kind of core-collapse supernova, aren't they?



Core collapse, but will pair instability core collapse result in a black hole, or unbund the star into a gas cloud?

Nereid
2011-Jul-08, 09:12 PM
And that (predicted, per theory) fate is ...?The stars of approximately solar mass can be seen completing their evolution. Not following a single star, astronomers are not that old, but the universe is slightly older than the total lifetime of the Sun. The old stars of globular clusters, and spread around Milky Way as well, include stars of roughly solar mass (initially), so the red giants are the brightest stars of globular clusters (and a nearby one is Arcturus).

Solar mass stars first fuse protium in their centre (main sequence) then protium around the centre (red giant branch) then helium in the centre (while continuing to fuse protium around - in horizontal branch) and finally helium around the centre (asymptotic giant branch). By that point they have shed most of their hydrogen envelope and do not fuse the remaining carbon core.

Brown dwarfs cannot sustain protium fusion and cool down into a cold body that, unlike a white dwarf, consists of protium rather than carbon.

Now, low mass stars sustain slow protium fusion. But when protium is exhausted, what is needed to start helium 4 fusion by triple alpha process?
Even for singletons things get complicated.

For a given mass and (low) metallicity, down to some low mass limit (but still ordinary stars, i.e. burning hydrogen - 'protium' - in their cores), a switch to helium core burning and hydrogen shell burning is certain. But at what mass/composition surface (surfaces? if the C/N/O ratios were to vary greatly, or if the star began life greatly enriched with Fe+ compared with CNO, or ... would the transition masses vary too?) does this happen (remember the OP's question)?

Then there's the mass/composition surface for radiative vs convective zones, and the extent to which 'dredge up' occurs (and the extent to which it makes any difference to the fate of a singleton star): below a particular mass (composition related? I'm sure it is!), a star will remain fully convective its entire life, which means it will burn almost all its hydrogen. At that point it will cool, just like a brown dwarf, except that the high pressure/low temperature phase state of its interior will be something quite radically different than has ever been produced in any lab (helium is a very unusual element in this regard)! But that will have no effect on its outward appearance, save for its mean density and radius (though doing whatever asteroseismology on dead stars will one day be called would give fascinating results).

So, as I said in an earlier post, the low mass fates are white dwarf (helium, carbon, oxygen, nitrogen? other??) or 'frozen Jupiters' (of many flavours, some of which are quite exotic objects under the surface).



Aren't they predicted to end as either neutron stars or black holes (or, possibly, quark stars)?

IIRC, they are a 'just' a different kind of core-collapse supernova, aren't they?
Core collapse, but will pair instability core collapse result in a black hole, or unbund the star into a gas cloud?
I don't know; off the top of my head, I can't think why the onset of pair instability would - or could - produce enough energy that could couple to the baryons to accelerate them all to escape velocity. I mean, in a regular core collapse SNe, most of the energy is released as neutrinos, which provide only momentary pressure against near-light-speed collapse of the core.

chornedsnorkack
2011-Jul-09, 07:52 AM
For a given mass and (low) metallicity, down to some low mass limit (but still ordinary stars, i.e. burning hydrogen - 'protium' - in their cores),
It is important to specify protium, because deuterium is hydrogen, too.


Then there's the mass/composition surface for radiative vs convective zones, and the extent to which 'dredge up' occurs (and the extent to which it makes any difference to the fate of a singleton star): below a particular mass (composition related? I'm sure it is!), a star will remain fully convective its entire life, which means it will burn almost all its hydrogen.
What will increasing concentration of helium and decreasing concentration of hydrogen, and increasing temperature, do to convective stability?


At that point it will cool, just like a brown dwarf, except that the high pressure/low temperature phase state of its interior will be something quite radically different than has ever been produced in any lab (helium is a very unusual element in this regard)! But that will have no effect on its outward appearance, save for its mean density and radius (though doing whatever asteroseismology on dead stars will one day be called would give fascinating results).

So, as I said in an earlier post, the low mass fates are white dwarf (helium, carbon, oxygen, nitrogen? other??) or 'frozen Jupiters' (of many flavours, some of which are quite exotic objects under the surface).



Brown dwarfs and white dwarfs are both cool bodies supported by degeneracy pressure. The difference now is that brown dwarfs are below 0,08 solar masses and white dwarfs are above 0,5 solar masses. No cool bodies between 0,08 and 0,5 solar bodies have formed yet - but in future they should.

Nereid
2011-Jul-09, 12:33 PM
It is important to specify protium, because deuterium is hydrogen, too.
Ah, so that's why you used that word! Neat. :cool:

I might start using that convention myself; up to now, I've always used 'hydrogen' for 1H, and deuterium for 2H.


What will increasing concentration of helium and decreasing concentration of hydrogen, and increasing temperature, do to convective stability?
A very good question, the answer to which I do not know. :clap:


Brown dwarfs and white dwarfs are both cool bodies supported by degeneracy pressure. The difference now is that brown dwarfs are below 0,08 solar masses and white dwarfs are above 0,5 solar masses. No cool bodies between 0,08 and 0,5 solar bodies have formed yet - but in future they should.
Ah, I see now.

I've been concentrating on from-the-Earth observables; only in a wide binary would it be possible to tell the difference between a Jupiter, a dead brown dwarf, and a dead low mass star (if you didn't know the age of object/universe, or where they were born, etc); the internal degeneracy pressure of these objects would show up only indirectly, in the effects of surface gravity on lines (and bands?) in the spectra, right?

And I agree that, in the case of singletons, there should be no such cool bodies; however, in a neutron star-white dwarf (WD) close binary, the former should strip mass off the latter, shouldn't it? Leaving a puny WD (or none at all - hence millisecond 'old' pulsars). Of course, such a WD may not be 'cool'. :razz: