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Black hole straight from cloud?

  1. Nov 20, 2014 #1
    Can be black hole created straight from cloud forming protostar.
    I mean, the region which is collapsing is so massive that pressure of radiation could not resist and the cloud is collapsing to singularity?
    If not, why?
     
  2. jcsd
  3. Nov 20, 2014 #2

    ChrisVer

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    I am not really sure whether that's possible, but I will try to make a guess, and maybe someone else can disprove or prove me correct...
    I say no, because things don't happen so fast and violently on their own, during the formation of a star (it starts just by the gravitational pull of a very small denser cloud of atoms) . Since the star is forming by a cloud of mainly Hydrogen (and other light nuclei), it will eventually get into burning it and avoiding its collapse... maybe if it is very massive, it's going to burn it all up much faster but it will have to burn it before collapsing... That's why the massive stars don't live so long as the less massive do...
     
  4. Nov 20, 2014 #3
    I understand, I mean no also, but I dont know why. Ok I dont want to say it collapses in 10sec. But it starts burn and gravitational force is higher than this which coming from radiation. It has too collapse more and more burn more and more but radiation is still weaker. Maybe is not possible so massive collapsing region in the cloud...I don know.
     
  5. Nov 20, 2014 #4

    ChrisVer

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    As I said I am not an expert, but I suspect for something like this to occur that you have a violent formation of a star. Instead the stars are formed by small inhomogeneities within the dust cloud... then the rest of the cloud "collapses" around that dust and starts burning- this happens slowly and thus equilibrium can be achieved...
     
  6. Nov 20, 2014 #5

    Nabeshin

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    It is thought that this should happen, and in fact is a proposal for how one might generate intermediate mass (10^3<M<10^6 solar) black holes. The idea is called 'Direct Collapse' for black hole formation, if you want to read more about it.
     
  7. Nov 20, 2014 #6
    Thank you very much.
     
  8. Nov 21, 2014 #7

    Chronos

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    Direct collapse is a possibility still in play to explain the origin of supermassive black holes. Similarly, population III stars in the early universe could have been incredibly massive because the low/zero metallicity of precursor gas clouds would inhibit efficient transport of heat from contraction.
     
  9. Nov 21, 2014 #8
    III stars are the first formed stars? How do metals catalyze heat transport?
     
  10. Nov 21, 2014 #9

    Matterwave

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    Like many things in astronomy, the population numbers run backwards... the higher the population's number the lower the metallicity and therefore the older the star. Population III stars are the oldest stars with no metallicity at all beyond BB levels, the Sun is a population I star.

    When astronomers say "metals" we mean anything other than hydrogen and helium. These other elements help in heat transport because they are heated up and emit in infrared wave-lengths, to which molecular hydrogen and helium are transparent, making it easier to radiate away the heat generated by the collapse.
     
  11. Nov 23, 2014 #10
    One big problem for a direct collapse model is that the cloud of gas conserves angular momentum as it collapses. Unless the cloud has virtually no angular momentum to start with (unlikely) it will spin faster as it contracts. At some point, the gas becomes rotationally supported and will fragment rather than collapsing to a point.
     
  12. Apr 28, 2015 #11
    It depends of what do you mean by "straight"
    I've visited a star life span calculator here:
    http://www.asc-csa.gc.ca/eng/educators/resources/astronomy/module2/calculator.asp [Broken]
    Using this, I calculate:
    If "straight" you mean 1 seconds you would need a nebulae as massive as 10 millions solar mass.
    It will be in main sequence in only 1 seconds, and the rest should be shorter, too. Helium, CNO, silicon, iron burning, etc...
    10 millions solar mass is possible for a nebulae, star or a black hole. But not to a neutron star nor a planet.
    But for a 10 millions solar mass nebulae "straight" (1 seconds) into forming a star, only divine intervention needed :smile:. Not trying to bring religion in this discussion, here.
     
    Last edited by a moderator: May 7, 2017
  13. Apr 28, 2015 #12

    Drakkith

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    Stars can't get anywhere near this massive. They are limited to about 150-200 solar masses in the current era of the universe, and perhaps up to about 300-500 solar masses in the very early universe.
     
  14. Apr 28, 2015 #13
    Thanks for your answer Drakkith.
    Surely if the definition of a star is
    "any of the large, self-luminous, heavenly bodies, as the sun, Polaris, etc."
    http://dictionary.reference.com/browse/star?s=t
    Why can't a star get that massive. Even if for 1 seconds, 1 minutes or 1 year before it exhausts its main sequence and collapsing.
    A neutron star will collapse into a black hole at certain mass, right? I don't know the number, I'm not a physics, sorry.
    And a planet will star to burn its material at cetain mass or if it is composed higher than iron it collapse into a black hole, right?
    But it's just a tought experiment.
    Is it probable although not possible?

    Thanks for your earlier response.

    Steven
     
  15. Apr 28, 2015 #14

    Drakkith

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    It's not possible for a gas cloud of that kind of mass to collapse into a single star. And even if it were, the collapse of the cloud and later the star itself is limited by the rate of energy transport out of the core, through the stars inner layers, and out into space, all of which takes a significant amount of time. MUCH longer than seconds, minutes, or even years.

    Basically, in order to collapse, a gas cloud (or star, or gas giant, etc) has to get rid of the energy its particles accrue as they accelerate by falling towards the center, otherwise they just bounce off of each other and go right back up to where they were. It's like dropping a 'super ball' onto cement. If it weren't for the ball losing a small amount of energy during each bounce, it would never stop bouncing right back up to the same height. For the particles at the center of the collapsing mass, the energy must be transported out to the 'surface' and then radiated away into space. Since this process takes thousands of years for stellar sized objects, if not hundreds of thousands or more, it cannot collapse faster than that.

    Plus, the energy transport itself exerts pressure on the outer layers and can blow them completely off if the conditions are right. The most massive of stars are right at the edge of this limit and generate a very, very strong stellar wind that can blow something like several dozen solar masses of material away from the star over the course of its million-year lifetime.
     
  16. Apr 28, 2015 #15

    Vanadium 50

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    Using a calculator intended for a particular mass and lifetime far from that operating point (millions or trillions) is unlikely to produce anything useful.
     
  17. Apr 28, 2015 #16
    That's right Vanadium 50!
    As Drakkith says. Max star limit is 150 to 200 solar mass.
    Thanks for your correction.

    Steven
     
  18. Apr 28, 2015 #17
    It has been suggested that the collision of two or more massive, metal-poor, stars could, temporarily, exceed the Eddington limit. This would cause the newly created star to lose mass rapidly until hydrostatic equilibrium is achieved. Thus allowing for stars to exceed 200 solar masses briefly, such as the star R136a1 (RMC 136a1) which is currently 256 M. It is suspected that the star R136a1 started out with ~320 M, and has been continually losing mass ever since.

    It should also be noted that a 500 M main sequence star only has a lifespan of ~1,789 years before it collapses into a pair-instability supernova. For a black hole to form, a star must have less than ~130 M, and a 130 M main sequence star has a lifespan of ~51,897 years.
     
  19. Apr 28, 2015 #18

    Drakkith

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    That's a real fast burner!
     
  20. Apr 28, 2015 #19
    Is that true?. What if the star is more than 130 M, say ... 200 M. Can't a black hole be formed?

    Thanks for any answer.
     
  21. Apr 28, 2015 #20

    Drakkith

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