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Type of material of black holes

  1. Dec 23, 2007 #1
    I know that there exist 4 types of material: solid, liquid, gas and plasma. Black holes are also some kind of material and probably not one of the above. Then, how can we describe the material of black holes?
     
  2. jcsd
  3. Dec 23, 2007 #2
    degenerate

    ''characterized by atoms stripped of their electrons and by very great density <degenerate matter>; also : consisting of degenerate matter <a degenerate star>''
     
  4. Dec 25, 2007 #3

    chroot

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    ray b,

    That is incorrect -- black holes form only after all degeneracy pressures have been overwhelmed. Your quote applies to white dwarf and neutron stars, not black holes.

    Classically, black holes contain nothing more than singularities. All of their mess is confined to a single geometric point, and thus cannot be said to have a "phase" at all.

    - Warren
     
  5. Dec 26, 2007 #4
    This is highly speculative but I would be interested to hear other peoples opinions. Interestingly enough, I think of black holes as possibly being string-degenerate matter around the time of their creation. White dwarfs (created by the collapse of stars up to 10 solar masses) are electron-degenerate matter (the electrons in the atoms occupying every available quantum state) with a diameter of approx. 4000 miles. White dwarfs have a density of 10 tonnes/cm^3 and an escape velocity of 5,200 km/s. Neutron stars (created by the collapse of stars of 10+ solar masses) are neutron-degenerate (the electrons are forced into the protons, turning them into neutrons, basically turning the star into a huge atomic nucleus) with a diameter of approx. 6 to 12 miles. Neutron stars have a density of 80 million to 2 billion tonnes/cm^3 and have an escape velocity of half the speed of light which means were on the way to how a black hole behaves. There is the hypothetical quark star (the result of a collapse of a rapid spinning star, 10+ solar masses) which hasn't been detected but is suppose to be formed when the neutrons break down into quark-degenerate matter, forming a star that is basically a vast nucleon < 6 miles across. This would have an immense density and you can only guess at the escape velocity, anything from 150,000 up to (but not) 300,000 km/s. Now it gets very speculative. The next level (if string theory is correct) would be the collapse of quarks into string-degenerate matter (possibly created by the collapse of stars with 40 to 50 solar masses in a hypernova). Quarks might break down into string-degenerate matter, the other dimensions (which are often mentioned in association with string theory that collapsed shortly after the big bang, becoming tightly bound within quarks and electrons) would be revealed, causing the collapse of matter in any recognisable form, creating a singularity.

    Hopefully this speculation is within the Physics Forums policy, it's a notion that I've thought about on a couple of occasions and would be interested in other peoples opinions.
     
    Last edited: Dec 27, 2007
  6. Dec 31, 2007 #5
    I did some research regarding the above and would prefer to edit my first post but unfortunatly this can only be done in the first 24 hours. If there is an option to edit the post later than this, I'd appreciate it if someone could let me know. I've revised the text from the hypothetical quark star onwards-


    There is the hypothetical quark star (the result of a collapse of a rapid spinning star, 10+ solar masses) which hasn't been detected but is suppose to be formed when the neutrons break down into quark-degenerate matter through a process called quark deconfinement, forming a star that is basically a vast nucleon < 6 miles across. This would have an immense density and you can only guess at the escape velocity, anything from 150,000 km/s up to (but not including) 300,000 km/s (the speed of light). Short duration gamma ray bursts detected from space may be the concequence of quark novae (the collapse of neutron stars into quark stars).

    It now begins to get speculative. The next level would be the collapse of quarks into string-degenerate matter (possibly created by the collapse of stars with 20+ solar masses) creating a string star. Oddly enough, there is a hypothetical star called a preon star that is made of preon-degenerate matter. Preons are postulated 'point-like' particles conceived to be subcomponents of quarks and leptons and is an alternative theory to string theory (though some physicists believe that should preon theory be successful, it may be possible to formulate a version of string theory that gives rise to a successful model of preons). A preon-degenerate star would probably share some characteristics with a hypothetical string-degenerate star. Based on estimates, a preon star would have the density of 10^23 kg/m^3 (100 trillion tonnes/cm^3) and a maximum diameter of just 80 metres before the escape velocity would reach the speed of light (300,000 m/s) and the star would collapse into a black hole. Smaller preon stars might actually be candidates for dark matter.

    Now it gets very speculative. In the next level, the string-degenerate material (or preon-degenerate) would break down and the strings themselves would interact. The other dimensions (which are often mentioned in association with string theory as 'degrees of freedom' that collapsed shortly after the big bang, becoming tightly bound within quarks and leptons and can number from 10 to 26) would be revealed, causing the collapse of matter beyond any recognisable form. More than likely at this point, because of the colossal pressures induced by the collapse of a star of 20+ solar masses, the core would be crushed to a single point, creating a black hole (the event horizon governed by the mass of the collapsed material which can be calculated using the Schwarzchild radius).

    The collapse of large stars with a fast rotation may create a spinning black hole. As the core becomes smaller under pressure, it spins faster. This causes the sphere to flatten. Massive centrifugal forces cancel out the inward force of gravity and create a spinning ring of degenerate matter which eventually collapses into a ring singularity. This is also called a Kerr black hole (or Kerr-Newman black hole). It's believed that most black holes are like this in nature due to the fact that most stars spin.


    Steve
     
  7. Jan 9, 2008 #6
  8. Mar 15, 2008 #7
    I put together a basic blog regarding the potential of black holes having a Planck density core. Below is the introduction which talks about Schwarzschild black holes, the rest of the blog looks at Kerr rotating black holes and ring singularities with Planck density. If you find the below of interest, you're welcome to take a look at the full blog.


    Black Hole - Planck unit?

    Planck density* = 5.155x10^96 kg/m^3 = 5.155x10^90 kg/cm^3 = 5.155x10^87 tonnes/cm^3
    (Based on Planck mass, 2.176x10^-8 kg and Planck length, 1.616x10^-35 m).

    'This is a unit which is very large, about equivalent to 10^23 solar masses squeezed into the space of a single atomic nucleus. At one unit of Planck time (5.39121x10^-44 s) after the Big Bang, the mass density of the universe is thought to have been approximately one unit of Planck density.'
    (http://en.wikipedia.org/wiki/Planck_units)

    *Planck units are sometimes (humorously) referred to as 'God's Units' as they are based on the properties of free space and not on the properties of any prototype, object or particle (that could be thought of as arbitrarily chosen). They are also referred to as natural units because the origin of their definition comes only from properties of nature and not from any human construct. Some believe that any communication with extra-terrestrial intelligence would require such a system of units. There are 5 basic Planck units, the above shows Planck length, mass and time; the other two are charge (1.8755x10^-18 C) and temperature (1.41679x10^32 K). They were established in the early 20th century by Max Planck, who is considered the founder of quantum theory.

    The Schwarzschild radius of the sun is 2943 m. Based on an overall mass of 1.9891x10^30 kg, the density around about the point that the matter collapses into a black hole would be 1.863x10^13 kg/cm^3 (or 18 billion tonnes/cm^3). As the radius passes the Schwarzschild radius, light would begin to free fall towards the surface of the sphere, unable to escape from the gravity (the escape velocity for a sphere with this mass and radius would exceed 300,000 km/s, the speed of light), hitting the surface of the sphere, compacting the sphere further. It's possible the photons energy would convert to mass as it collides with the collapsing star, contributing further to the black holes overall mass. Reactions between particles often result in photons which escape stars when gravity allows it (leaving the particles marginally lighter), here the process would be reversed. It seems to be an accepted fact that photons are massless but have energy due to their high momentum, if they are captured, become still or collide heavily with something, they would transfer their energy as mass. In general relativity, the source of black holes are considered geometric singularities, in quantum mechanics, they are speculated as having Planck density (5.155x10^90 kg/cm^3), the maximum energy density allowing in current physics.

    Theoretical fundamental particles such as preons or strings are approx. 10^-33 m in size which are close to the Planck length, the smallest measurement currently used in physics (1.6x10^-35 m). If strings or preons are at the heart of all quarks and leptons, they would normally be at their closest (in ground state) ~10^-15 m (a Fermi), the distance between quarks within a nucleon. Possibly under great pressure the quarks would break down (approx. 10^20 kg/cm3) and under greater pressure, the preons/strings would break down also and the pure quanta of energy that reside at the very core of fundamental particles might compact to something in the region of Planck density.

    If the core of a star about the mass of our sun collapsed beyond the Schwarzschild radius (2943 m) then it's possible it could collapse all the way to Planck density. For a mass the size of the sun (1.9891x10^30 kg) this would result in a sphere with a radius of 4.516x10^-23 m or ~45 yoctometre (a yoctometre or ym is 10^-24 metres). For the supermassive black hole at the centre of our galaxy which is predicted to have a mass of 3.6 million solar masses (7.16076x10^36 kg), the core radius at Planck density would be 6.9217x10^-21 m or ~7 zeptometre (a zeptometre or zm is 10^-21 mteres), the Schwarzschild radius (event horizon) would be 1.0624x10^10 m (or ~10.6 million km - our Sun has a radius of 0.6955 million km).

    http://blog.myspace.com/index.cfm?f...n=FE2495B7-2B82-434B-9D3F53AF736D317640033268

    Steve
     
    Last edited: Mar 15, 2008
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