The Mystery Of Exploding Stars

Stars operate on nuclear fusion. The tremendous heat and pressure in the centers of stars crunch smaller atoms into larger ones, and the leftover binding energy is released as heat and light. Ordinarily, the electrons in atomic orbitals are not even considered as a factor in such nuclear reactions. However, I have concluded that it is actually electron repulsion that drives what takes place within stars.

A star is born when a vast amount of matter in space coalesces by gravity into a compact mass. The matter is usually dust and gas, but does not have to be of any particular elements. The difference between a star and a planet is that stars have enough mass so that the gravitational pressure at the center is enough to overcome the electron repulsion between atoms so that it crunches smaller atoms together into larger ones.

There is less nuclear binding energy in the nucleus of the one larger atom then there was in the two smaller atoms and the kinetic energy in the gravitational  mass of the star which fused them together so that the excess energy is released. It is this released excess energy that makes the star shine. A star reaches an equilibrium in which the inward force of gravity is balanced by the outward energy from the nuclear fusion at it's core.

Remember that the universe, at it's most fundamental level, is composed of electric charges. There are two such charges, negative and positive. The rules are that opposite charges attract, while like charges repel. Nuclear binding energy is the energy which overcomes the mutual repulsion of the like-charged positive protons in the nucleus to hold the nucleus together. This is accomplished by the presence in the nucleus of neutrons, which have a neutral electric charge. An element is defined by the number of protons in the nucleus, but the heavier elements get the more neutrons there are in the nucleus relative to the number of protons.

Electron repulsion is what keeps atoms from merging in to one another, since atoms are mostly empty space. The atoms in orbitals around the nucleus in adjacent atoms are all negatively-charged so that the like-charge repulsion prevents atoms from merging together.

In the posting on this blog, "The Chemical-Nuclear-Astronomical Relationship" , we saw how the difference in magnitude between the energy released in a chemical reaction as compared with a nuclear reaction is the same as the difference in magnitude between the mass where a sphere forms in space by gravitation and the mass at which nuclear fusion ignites to form a star.

What I would like to explain today is my conclusion of how it is the electron repulsion between atoms that actually governs the processes within stars. The largest stars tend to eventually explode in a supernova, scattering it's component matter across space so that planets and second-generation stars might form from it. But why should a star shine for billions of years, with no significant changes in matter added or subtracted to it, and then suddenly explode?

Exploding stars are not at all arcane to us because you would not be reading this without such a supernova, as every atom in your body as well as in our solar system, was once part of a star which exploded. The gravitational collection of matter to form the star is relatively simple so, with no new information added, the life cycles of stars must also be relatively simple. It is my finding that the operation of stars, as well as the explosions as nova and supernova, and also the binding energy curve of atomic elements, can be explained by simple geometry and electron repulsion even though electrons do not usually even count in nuclear reactions.

In the posting on this blog, "Electron Repulsion And Density", I gave my version of why all matter is not of the same density. The analogy that I used was the filling of a box with ball bearings. A ball bearing is a small solid metal sphere, usually made of steel, and used in the construction of various machines which have rotating axles.

The box should end up weighing the same no matter what size of ball bearings it is filled with, as long as the ball bearings are of the same density and fit neatly into the box and are all in each box are of the same size. I did not fill boxes with ball bearings to test this, but I did calculate it mathematically.

The implication of this is that all materials should be of the same density, at least those of the same state of matter such as solid or liquid. Yet this is most certainly not the case, materials made of smaller atoms tend to be of lower density than those made of larger atoms. The only way to explain this is the electron repulsion between atoms. The same mass in smaller atoms would have more total surface area than the mass in larger atoms, and this would mean that there would be more total surface area with the smaller atoms and thus more total electron repulsion between atoms, bringing about more space between atoms and thus lower density.

(Another result of electron repulsion is weight. As we saw in "The Weight Hypothesis", on the physics and astronomy blog, weight is a manifestation of a hindering of gravitational attraction on matter by the electron repulsion between atoms).

Electron repulsion between atoms is the very definition of a star. The fusion that takes place would not make sense except that fewer larger atoms take up less space, and so relieves the tremendous gravitational pressure, than more smaller atoms. This is due to electron repulsion because of the principle that a box of ball bearings will weight about the same, containing the same amount of mass, regardless of the size of the bearings. Heat energy assists the process, but gravity must get it started. More atoms fuse with the addition of heat, accelerating the process, than would have fused by gravitational pressure alone.

We could describe the equilibrium of a star in the form of an equation: STAR = GRAVITY + RELEASED BINDING ENERGY > ELECTROMAGNETISM. This defines a star in terms of the basic forces of physics, with electromagnetism representing the electron repulsion between atoms. A star exists when the inward force of gravity of the mass, plus the released binding energy from fusion, is greater then the force of electromagnetism in the form of electron repulsion. Basically, a star shines when there is enough mass pulled together by gravity to overcome the electron repulsion between atoms and crunch small atoms together into larger ones, which releases the excess binding energy.

There is a limited zone in the center of a star where fusion takes place, it does not occur throughout the star. The heavier atoms naturally tend to move toward the center of the star, although the heat at the center forms upward convection currents, and it is in the center where heavier elements are formed from the lighter ones by fusion. Heavier elements in a second-generation star, which is one that has collected back together by gravity from the debris of a supernova, have a cooling and life-lengthening effect on the star because it takes more energy to move these heavier atoms. Astronomers often refer to heavier elements as "metals", even though not all are technically metals.

The so-called "binding energy curve" of atoms is a chart of the phenomenon of how the binding energy per nucleon in atoms increases sharply until we reach the element iron, then is slowly decreases as we move to heavier elements. A nucleon refers to either a proton or a neutron in the nucleus of an atom. Atoms up to iron and nickel are formed by the usual crunching together of lighter atoms into heavier ones by fusion within the core of the star. Elements heavier than this are formed only during the brief time that the star is actually exploding as a supernova, because some of the energy of the explosion goes into binding the heavy nuclei together.

This is why the heavier elements are much more rare than those up to iron. The nuclei of some heavier elements, having been put together by the sudden burst of energy in a supernova, are not entirely stable and give off radiation or may gradually break down. This is known as radioactivity. The usual crunching process is referred to as the s-process (for slow) and the fusing of heavier nuclei during the actual supernova explosion as the r-process (for rapid).

The heaviest element that occurs naturally is uranium, with 92 protons, but heavier elements can be formed in nuclear reactors. When atoms of plutonium or the U-235 isotope of uranium are split by nuclear fission, in a nuclear reactor or bomb, we get back the energy of the long-ago supernova which put the atoms together in the first place. The upper limit to the elements is because even the energy released by a supernova, which can fuse nuclei, has it's limits.

The crunching process peaks at iron, which has the greatest binding energy per nucleon of any atom. The reason for the binding energy curve, the increase in binding energy per nucleon up to iron, is simple. As atoms are crunched together step by step, the binding energy is still in the nucleus from the step before.

Hydrogen, the simplest atom with only one proton and one electron, is crunched together to form helium which has two protons and two neutrons. Most of the energy in sunshine is from the leftover binding energy when four hydrogen atoms are crunched together to form one helium atom. Two of the electrons in the hydrogen atoms are also crunched into protons to form neutrons.

Then three helium atoms can be crunched together to form a carbon atom, or four helium atoms to form an oxygen atom. Each step also includes the added binding energy from the step before so that the more steps there have been to form an atom by crunching, the more binding energy per nucleon there will be, and this peaks at iron. The energy that is transformed into binding energy comes from the gravitational pressure on the atoms, which causes them to fuse, and which came from the previous supernova if it is a second-generation star, or from the Big Bang itself.

However, there is a consequence of crunching smaller atoms together into larger ones. Larger atoms have more electrons, and thus it would take more force to overcome the electron repulsion of these larger atoms in order to fuse them together into still larger ones. This explains why most stars simply burn out eventually, it is only the largest stars which explode into a supernova.

Although the star fuses lighter atoms into heavier, no new mass is ordinarily being added and the star eventually reaches a point where there is not enough gravitational pressure to fuse the heavier atoms which it has created together. The star goes dim and then ceases to shine altogether. This should happen around when the fusion process has already created a lot of iron.

But what if the star is large enough, with enough gravitational pressure on the center, to continue crunching smaller atoms into larger ones past the point where smaller stars would have been unable to and would have burned out? There turns out to be a different consequence.

The larger the atoms get, the more rapidly they can be crunched together, per nucleon, in the center of the star. This must mean that more energy is being released as the star progresses to crunching heavier elements together. Also, there actually is more binding energy per nucleon, as per the binding energy curve, which would be released as the star progressed to fusing heavier elements together as long, of course, as the star was large enough to have the gravitational pressure necessary to fuse the larger atoms together.

This increase in energy output from the core upsets the equilibrium of the star because it is a balance between the inward pressure of gravitation and the outward pressure of the binding energy being released by fusion in the center of the star. The outward pressure is no longer balanced by the inward pressure of gravity and this creates an explosion. The star attempts to regain equilibrium by blasting away it's outer layers in order to reduce still further the pressure on the core which is generating the fusion. This blasting away of the outer layers of a star is what we refer to as a nova.

If the nova does not succeed in slowing the release of energy at the center then the imbalance between inward and outward pressure becomes still greater because of the mass that is now removed from the star.. The star explodes from the center in the grand finale known as a supernova. It scatters it's mass across space, which may coalesce back together by gravity into a second-generation star such as the sun, which already contains heavy elements and which can have a system of planets around it which also require heavy elements to form a compact and solid structure.

The internal processes do vary somewhat from one star to another, but the processes do have a basic similarity and I think that this model of those processes actually being governed by electron repulsion holds true for all stars.