Black holes are are mystery for many of us. I was always astouned when i watched documentations about black holes.
In “The Circle of Life,” it is described how stars are born, die, and are reborn. However, we did not discuss what happens to the material that is left over after the star’s destruction – the star core.
Circle described electron degeneracy and its effect on star performance. After the energy is released in a supernova event, gravity takes over again. However, this time the electron forces can’t stop the star core’s collapse.
Past electron degeneracy, there are two further stages and, subsequently, two further options for the star core. If the residual core is 1.3-1.9 stellar mass units, then neutron degeneracy will support the collapse and balance out gravitational forces. No further collapse will occur and the star will stabilize – a neutron star will be born.
Astro 101: Black Holes
What are black holes? Do they exist in reality? How are they created? What is their connection to stars? What would happen if one were to fall in? Could it also function as a wormhole or a time machine?
A residual core greater than 2.0 stellar mass units without fusion, will create an easily explained, yet mysterious phenomenon called a black hole. Past electron and neutron degeneracy the core will uncontrollably collapse past the Schwarzschild radius (or Event Horizon) and create the mysterious Black Hole.
According to an international team of astronomers, led by Dr. Eugene Churazov and Dr. Rashid Sunyaev, and the Space Research Institute, Moscow; “astronomers believe there are tens of millions of active black holes spread throughout space…”
What are black holes?
Dr. Nicholas White, Director of the Astrophysics Science Division at NASA’s Goddard Space Flight Center, says “…black holes are really just the evolutionary end point of massive stars.” All black holes comply with the 1st and 2nd laws of thermodynamics and are therefore easily calculated.
Three basic types of black holes exist: stellar-mass (2-20 solar masses), intermediate-mass (> 1,000 solar masses) and super-massive black holes (millions-billions of solar masses). Yet no matter what the size of the black hole, there is no outward force to stop the gravitational forces from collapsing the star. The collapse will continue until a singularity is reached. This is a point where the volume of the star’s core is zero and its density is infinite. The gravitational forces are so great that light photons can not escape the event horizon and thus direct visual observation of the singularity is impossible.
The Point of No Return
Black holes have several unique qualities that many find difficult to understand: the concept of the photon sphere, an event horizon, and more difficultly, that point or singularity.
The event horizon is nothing more than the radius of a particular sphere. The actual radius of any particular sphere depends on the mass of the core. The Event Horizon is easily calculated and basically lies at 3 times the solar mass of the core in kilometers. A core 10 times our sun is a 10 solar mass black hole with a Schwarzschild radius of 30 km.
The Photon Sphere is that point where gravitational forces bend light photons at an equal distance around the center of the star’s core. According to Dr. Robert Nemiroff, Professor of Astronomy and Astrophysics at the University of Pennsylvania and Michigan Technical Universities, in the photon sphere “… you can see the back of your head.”
The photon sphere in a non-rotational core is 3/2 times the event horizon radius. A core 10 times our sun is a 10 solar mass black hole with a Schwarzschild radius of 30 km and a Photon Sphere of 45 km.
The Singularity is a phenomenon that requires discussion well above the scope of this article. What happens prior to and at the singularity is a matter for the String Theory debate. Suffice it to say, the singularity is beyond the event horizon, where the escape velocity of light is greater than the gravitational force of the black hole. A point where conventional laws no longer apply and space-time is distorted.