How are super-massive stars formed?

[EWyatt]

As we know, stars are born when they fuse hydrogen, then continue with that long fusion process. This ignition would "seem" to come at a standard model size during the star's formation. So how do some stars like Eta Carinae, R136a1, and even larger stars get so huge? Is the answer simply that they keep sucking in more and more matter from the local system after the initial ignition? Simple as that? Or is the star's eventual size somehow determined during its initial formative stage? Thnx....

[questionposter]

As we know, stars are born when they fuse hydrogen, then continue with that long fusion process. This ignition would "seem" to come at a standard model size during the star's formation. So how do some stars like Eta Carinae, R136a1, and even larger stars get so huge? Is the answer simply that they keep sucking in more and more matter from the local system after the initial ignition? Simple as that? Or is the star's eventual size somehow determined during its initial formative stage? Thnx....

 

Well first they have a larger amount of mass or matter to start with, and because they are so huge, they put so much more pressure on the hydrogen that they fuse it at a much faster rate than our sun, which releases more thermal energy causing the star to expend more.

[EWyatt]

Well first they have a larger amount of mass or matter to start with, and because they are so huge, they put so much more pressure on the hydrogen that they fuse it at a much faster rate than our sun, which releases more thermal energy causing the star to expend more.

 

 

 

Thanks for the reply, however, I was asking about those massive stars during their main sequence (much prior to red giant stage). And again, I suppose all/most stars "ignite" at about the same size, but get larger simply by eating up more matter. The early solar system of our sun apparently didn't have a lot of matter to digest, thus its smaller size.

[Airbrush]

Thanks for the reply, however, I was asking about those massive stars during their main sequence (much prior to red giant stage). And again, I suppose all/most stars "ignite" at about the same size, but get larger simply by eating up more matter. The early solar system of our sun apparently didn't have a lot of matter to digest, thus its smaller size.

 

There is just more matter in the vicinity of a giant star. Even after the star ignites, it can continue to grow from planets, asteroids, and even binary companion stars crashing into it. Most stars are smaller than our Sun, and very few are larger than 100 solar masses. This tells us the size of stars is limited by the amount of gas and dust in their immediate area.

Edited April 25, 2012 by Airbrush

[StringJunky]

http://physicsworld.com/cws/article/news/2009/jan/15/how-massive-stars-form

[granpa]

And again, I suppose all/most stars "ignite" at about the same size, but get larger simply by eating up more matter.

 

no.

they ignite at the same pressure.

but stars that form more quickly are hotter and therefore less dense and the pressure inside is less so they can grow larger before igniting.

 

supermassive stars form in the centers of the largest molecular clouds.

Edited April 26, 2012 by granpa

[questionposter]

That clump theory seems to make more sense to me. If you think about it, solar wind doesn't really blow rocks away, so the many rocky objects that would have also formed while the star was forming could be remaining even after the star's 20-solar mass fusion process has blown away much of the accretion disk.

[space noob]

Larger stars like the vy canis majoris, become so large by exerting their energy faster, canis is the largest star known and probably has the shortest life span of any other known star, lasting merely millions of years

 

I think the clump theory also explains large stars the best

Edited May 9, 2012 by space noob

[Airbrush]

Larger stars like the vy canis majoris, become so large by exerting their energy faster, canis is the largest star known and probably has the shortest life span of any other known star, lasting merely millions of years

 

I think the clump theory also explains large stars the best

 

I looked up this giant star on wiki and it only tells how large it is, about 2,000 times the Sun's diameter. It doesn't tell how many solar masses it is.

 

http://en.wikipedia.org/wiki/VY_Canis_Majoris

 

The most massive star is believed to be R136a1 (I wish it had a massive sounding name like Gigantor) was discovered in 2010, at 265 solar masses. And wiki doesn't tell you how large it is in solar terms (radius, diameters), funny that.

 

http://en.wikipedia.org/wiki/R136a1

[imatfaal]

AirB

 

Wikipedia has the details of the stars in a side bar on the RHS. I think you are both right - one is the the most massive and the other has the greatest radius.

 

 

R136a1 is a blue hypergiant star and the most massive star known.

 

 

Mass 265 M_☉

Radius 35.4 R_☉

Luminosity ≈ (8.7)×10^6[2] L_☉

Temperature 53,000 ± 3,000^[2] K

 

 

VY Canis Majoris (VY CMa) is the largest known star and also one of the most luminous.

 

Mass ~30-40 M_☉

Radius ~1,800-2,100 R_☉

Luminosity ~450,000^[L_☉

Temperature ~3,000K

[Airbrush]

Thanks imatfaal for the info. Now I just figured out the fancy notation. The mass of VY Canis Majoris is 30 to 40 solar masses. And the most masssive star is 35 times the radius (or diameter) of the Sun.

[imatfaal]

Air B - ah, I should have explained. We use a dot in a subscript like this for solar comparisons [imath] Mass_{\odot} [/imath] and a plus in subscript for earth comparisons [imath] Mass_{\oplus}[/imath]

 

These come from the old planet symbols that have been in use for many years

 

http://www.fourmilab...help/icons.html

[Airbrush]

Very interesting symbols, thanks for the link. I should memorize those.

[space noob]

Eh? So vy canis majored is bigger but it has a smaller mass than R136a1? Would that be because vy canis majoris is nearing the end of it's life and R136a1 is young?

[imatfaal]

Eh? So vy canis majored is bigger but it has a smaller mass than R136a1? Would that be because vy canis majoris is nearing the end of it's life and R136a1 is young?

 

I think that is right - but I am not sure. The Wiki article does state that vy Canis Major was a Blue O-Type star in the past and is close to going hypernova - so I think your idea is correct. I would have to do a lot of reading to be sure though

[fertilizerspike]

As we know, stars are born when they fuse hydrogen, then continue with that long fusion process. This ignition would "seem" to come at a standard model size during the star's formation. So how do some stars like Eta Carinae, R136a1, and even larger stars get so huge? Is the answer simply that they keep sucking in more and more matter from the local system after the initial ignition? Simple as that? Or is the star's eventual size somehow determined during its initial formative stage? Thnx....

 

To date nobody has demonstrated the fusion process said to take place in stars. Not only that, but stellar fusion models explicitly state that stars are self-compressed balls of gas. We know from the known properties of all gases that this is impossible. Gases under no circumstances compress themselves under their own weight while heating up, they expand to fill the available space while cooling. As for a star's size, I'd say it depends on at least two things; the amount of available matter and the magnitude of electric current that formed the star in a "z pinch".

[imatfaal]

!

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fertlizerspike

 

The main fora are for questions, answers, and debates rooted in mainstream accepted science. We have a whole forum - Speculations - in which you can promote your own new theories or discuss perceived problems with our present state of knowledge. As almost all your posts are arguing that we have huge flaws in modern physics perhaps you should post a few of your counter-arguments in that forum - but be aware you will have to defend your position with evidence rather than rhetoric.

 

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[MigL]

Do all stars really ignite at the same temperature, or pressure, as has been suggested ?

 

I would think the make-up of a star would be a big factor. A blue giant as opposed to a red giant, population I as opposed to population II, hydrogen rich as opposed to helium rich, or spiral arm location as opposed to galactic core location. A core with a high percentage of helium will require a much higher temp to ignite and I would assume, as a result, that red giants would be much more common than blue giants.

Edited April 4, 2013 by MigL

[Dishmaster]

The formation process of high mass stars is an active topic of research that is far from closed. The current paradigm is that high mass stars form in a similar way as normal low mass stars, i.e. by accretion of matter from a circumstellar disk. However, the merging of stars cannot be ruled out completely, although it might be rare compared to other scenarios.

 

An interesting and important observational fact is that high mass stars are NEVER formed in isolation, i.e. they always form in clusters, together with a lot of other stars, while the mass distribution follows the Salpeter law. A very interesting process that is being brought forward is the "competitive accretion" scenario. This basically says that the inital stellar embryos are more or less the same, but during the formation of a stellar cluster, they compete in accreting their mutual pre-stellar reservoir. Some of them manage to receive more than others, and thus grow bigger.

 

Now, the very special thing about high mass stars is that they continue to accrete matter even after igniting the fusion process in the stellar core. That has been a big puzzle for decades, because it was not conceivable how that was possible given the intense stellar winds blowing everything away. A way out was the modelling of star formation in 3D, and not as a symmetric spheroid. The lack of computing power had prevented such studies. Thus, it turned out that the surrounding circumstellar disk was less affected by the winds than previously thought. Most of the energy is released along polar directions, allowing the accretion process to proceed. This is known as the "flashlight effect".

 

One must also understand that very massive stars are very unstable, i.e. they can oscillate between a main-sequence-like state and a red giant state. So, the radius and the effective temperature of a very massive star may be a transitional phase. See: https://en.wikipedia.org/wiki/Luminous_blue_variable

[a_lexios]

 

To date nobody has demonstrated the fusion process said to take place in stars. Not only that, but stellar fusion models explicitly state that stars are self-compressed balls of gas. We know from the known properties of all gases that this is impossible. Gases under no circumstances compress themselves under their own weight while heating up, they expand to fill the available space while cooling. As for a star's size, I'd say it depends on at least two things; the amount of available matter and the magnitude of electric current that formed the star in a "z pinch".

All of the stars in our universe are alive. Their life is bound to the proper beating of their hearts, just like humans and their life's "juice" is the power of nuclear fusion that takes place in their core converting hydrogen to helium - ( Proton fusion, *protons are hydrogen nuclei.)

Protons repel each other normally because of their positive charge, but in temperatures exceeding 10.000.000 K, the particles embed so much kinetic energy that the electrostatic repulsion can be overcome. Once in close range the strong nuclear force takes over, pulling the protons together and initiating proton-proton fusion (P-P fusion). One of the protons changes into a neutron, and the resultant nucleus is called a deuteron (one proton and one neutron). The excess positive charge is expelled in the form of a positron (e+ , antimatter for electron) which collides with any close-by electron and annihilate each other. The excess momentum is expelled in the form of a neutrino.

The p-p fusion is a highly exothermic reaction thus creating an outward flow of energy. This outward "thermal pressure" balances the gravitational pull of the mass of the star that tends to make it collapse on itself and there we have it: A very active balance of opposing forces that keeps our stars alive and shining until interrupted. The so-called hydro-static equilibrium...

Now, for as long as a given star has enough fuel (hydrogen) to keep it's thermal pressure in the level required to balance it's gravitational pull, the equilibrium is preserved. At some point when the core runs out of hydrogen fuel, it starts contracting under the crushing force of gravity and depending on the overall mass of the progenitor star, we have various resulting formations - from white dwarfs to black holes.

Edited August 9, 2013 by a_lexios

[a_lexios]

 

All of the stars in our universe are alive. Their life is bound to the proper beating of their hearts, just like humans and their life's "juice" is the power of nuclear fusion that takes place in their core converting hydrogen to helium - ( Proton fusion, *protons are hydrogen nuclei.)

Protons repel each other normally because of their positive charge, but in temperatures exceeding 10.000.000 K, the particles embed so much kinetic energy that the electrostatic repulsion can be overcome. Once in close range the strong nuclear force takes over, pulling the protons together and initiating proton-proton fusion (P-P fusion). One of the protons changes into a neutron, and the resultant nucleus is called a deuteron (one proton and one neutron). The excess positive charge is expelled in the form of a positron (e+ , antimatter for electron) which collides with any close-by electron and annihilate each other. The excess momentum is expelled in the form of a neutrino.

The p-p fusion is a highly exothermic reaction thus creating an outward flow of energy. This outward "thermal pressure" balances the gravitational pull of the mass of the star that tends to make it collapse on itself and there we have it: A very active balance of opposing forces that keeps our stars alive and shining until interrupted. The so-called hydro-static equilibrium...

Now, for as long as a given star has enough fuel (hydrogen) to keep it's thermal pressure in the level required to balance it's gravitational pull, the equilibrium is preserved. At some point when the core runs out of hydrogen fuel, it starts contracting under the crushing force of gravity and depending on the overall mass of the progenitor star, we have various resulting formations - from white dwarfs to black holes.

 

 

**P.S: And if we want to be 100% on point; actually there is a force which could really inhibit

the gravitational collapse, once it has begun, and even if we do not have any sufficient

thermal pressure to counter the gravitational pull: Degeneracy pressure.

(More on that http://en.wikipedia.org/wiki/Electron_degeneracy_pressure )

[Moontanman]

 

All of the stars in our universe are alive. Their life is bound to the proper beating of their hearts, just like humans and their life's "juice" is the power of nuclear fusion that takes place in their core converting hydrogen to helium - ( Proton fusion, *protons are hydrogen nuclei.)

Protons repel each other normally because of their positive charge, but in temperatures exceeding 10.000.000 K, the particles embed so much kinetic energy that the electrostatic repulsion can be overcome. Once in close range the strong nuclear force takes over, pulling the protons together and initiating proton-proton fusion (P-P fusion). One of the protons changes into a neutron, and the resultant nucleus is called a deuteron (one proton and one neutron). The excess positive charge is expelled in the form of a positron (e+ , antimatter for electron) which collides with any close-by electron and annihilate each other. The excess momentum is expelled in the form of a neutrino.

The p-p fusion is a highly exothermic reaction thus creating an outward flow of energy. This outward "thermal pressure" balances the gravitational pull of the mass of the star that tends to make it collapse on itself and there we have it: A very active balance of opposing forces that keeps our stars alive and shining until interrupted. The so-called hydro-static equilibrium...

Now, for as long as a given star has enough fuel (hydrogen) to keep it's thermal pressure in the level required to balance it's gravitational pull, the equilibrium is preserved. At some point when the core runs out of hydrogen fuel, it starts contracting under the crushing force of gravity and depending on the overall mass of the progenitor star, we have various resulting formations - from white dwarfs to black holes.

 

 

Stars are alive? By what definition are stars alive?

[a_lexios]

 

Stars are alive? By what definition are stars alive?

 

 

Well, please allow me to put that part of the statement in quotes; your question will immediately answer itself:

 

[ All of the stars in our universe are "alive". ]