The Structure of Black Holes

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  • The Singularity:  This is the region of the black hole where all the mass of the black hole has been compressed down to nearly zero volume.  As a result the singularity has almost infinite density and creates an enormous gravitational force

  • The Event Horizon:  This is the "point of no return".  Any object, even light, that is within this radius cannot escape the gravitational pull of the black hole

  • The Schwarzschild Radius: This is the event horizon's radius.  It is the radius at which the escape velocity is equal to the speed of light,

    • R = 2GM/c2

  • The Accretion Disk:  This is a disk composed of stellar material that is spiraling towards that black hole

  • The Ergosphere:  If the black hole is rotating, then as it spins, its mass causes the space time around the black hole to rotate as well.  This region is called the ergosphere. 

  • Jets of Gas: For some black holes high intensity magnetic fields are emitted perpendicular to the accretion disk.  This causes charged particles to circle these magnetic field lines and creates jets of gas perpendicular to the acceleration disk.

 

 

        
    
For More Details Read Below

    
          A black hole is made up of several different parts.  Located at the very center of the black hole is the singularity.  This is the location of extremely large mass and almost zero volume, creating a point of infinite density [7].  Outside the singularity is the event horizon.  This is the radius at which if matter or light gets any closer, it cannot escape the gravitational pull of the black hole.  The event horizon is defined as the point at which the escape velocity of a particle would have to equal the speed of light [7].  So, anything within the event horizon’s radius is doomed to be pulled into the black hole.  Thinking about black holes as actually bending space, then “inside the event horizon there are literally no paths in space and time that lead to the outside of the black hole: No matter what direction you went, you would find that your path led back to the center of the black hole, where the singularity is found” [7].

          Another name for the radius of the event horizon is the Schwarzschild radius.  This is the radius away from the black hole such that the escape velocity equals the speed of light [2].  Therefore, the Schwarzschild radius can be thought of as the “point of no return” since once passed this point, nothing can escape the gravitational pull of the black hole.  Using the equation of escape velocity, vescape= (2GM/R)(1/2)  the Schwarzschild radius for a photon can be calculated.  To find the Schwarzschild radius one simple uses the speed of light as the escape velocity [2].  By setting vescape equal to the speed of light c, then:

        vescape = (2GM/R)(1/2) 

        c = (2GM/R)(1/2) 

        c2 = 2GM/R

        and R = 2GM/c2.

So, once an object, even a beam of light, is closer to the black hole than a radius of 2GM/c2 then there is no escaping the black hole’s gravitational pull.

 

          Outside the event horizon lays the accretion disk.  This is formed by stellar materials that are close to the black hole and are spinning toward the center, continuously pulled by the force of gravity [8].  As these particles spiral towards the singularity they collide and heat up, emitting x-rays [8].  If the black hole is rotating, then an area called the ergosphere also exists.  The ergosphere is a rotating region where “the black hole drags space itself” [9].  The mass of the black hole is so great and the force of gravity so strong that the space time around the rotating black hole is dragged along and moved, a phenomenon called frame dragging [9].

            On some black holes, jets of gas are also emitted perpendicular to the accretion disk.  The current best explanation for this is the theory that there are powerful magnetic fields being emitted from the black hole [8].  So, these jets of gas are the result of charged particles orbiting these magnetic fields being emitted from the black hole [8].

 

 

 

 

 

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