Why are we so fascinated by the stars? Some of our ancestors thought stars were gods. Still others thought the stars were angels pouring forth virtue upon the Earth. Contemporary scientists refer to stars as giant balls of gas.
The need to orient ourselves with respect to the stars continues, but the way that twenty-first century humans approach this challenge includes a growing base of knowledge about the stars that previous generations did not enjoy. Perhaps the most significant discovery is that stars are self-organizing processes. They are not just unchanging bright objects in the night sky. Stars proceed through stages of development that enable their radiance to come forth.
What is the ultimate origin of a star’s radiance? It comes from the intense compression of matter under the force of gravity. But what is the origin of this gravity? Strictly speaking, gravity is an effect of mass. Consider a vast cloud of hydrogen and helium that is destined to collapse into a future star. The gravitational attraction that causes the cloud to implode is generated by the mass of the cloud itself. In other words, the mass of the future star creates the gravity necessary to give birth to the star itself. In that sense, each star is a self-generating event.
And stars not only shine. They resonate, they communicate. Humans throughout history on every continent and in every culture have been stunned by the presence of stars in the vastness of the night sky. They have meditated on the beauty of the Big Dipper. So deeply moved by the majesty of the constellations and by the ineffable majesty emanating from the brilliance of stars, many have built their lives around them. They have imagined ways of not only organizing their personal lives but even patterning civilizations around the beauty and order found there.
In many cultures throughout history humans intuited that they descended from the stars, even before they had the empirical evidence from science that our bodies were formed by the elements forged by the stars. Humans felt something in the depths of the night as they contemplated the presence of the stars. They began to suspect that the meaning of their lives went far beyond what preoccupied them during the urgencies of the daytime world. They knew in their hearts that their journey and the radiance of the stars were interwoven.
The essence of the universe story is this: the stars are our ancestors. Out of them, everything comes forth. The stars are dynamic entities. They have a birth. They go through a development. They come to an end, sometimes a dramatic end. Here’s their story.
The birth of a star begins with a cloud of hydrogen and helium imploding under the influence of gravity. The cloud shrinks moment by moment. As the atoms draw themselves together into ever-tighter spaces, they collide and vibrate with energy. After each collision they gradually heat up. Even a cloud that starts out at temperatures hundreds of degrees below zero will slowly become warmer as the eons pass.
During this increase in temperature the process of star birth recapitulates processes that were active at the time of the origin of the universe. As the clouds of hydrogen and helium heat up to several thousand degrees, the atoms begin to melt down. The hydrogen atoms dissolve back into being protons and electrons, which then move about in the core of the protostar as freely interacting elementary particles.
The culminating moment, the very birth of the star, takes place when the temperature reaches ten million degrees. When the elementary particles get this hot they fuse into new stable relationships. This is similar to what took place in the early moments of the universe when the first nuclei were formed. The star thus has the capacity to activate creative processes that were at work billions of years ago. Such originating creativity is woven through space and time, waiting to be ignited. Humans in every culture have invented myriad ways in which this primal creativity could be accessed for the collective human journey.
For stars, creativity depends on maintaining a state of disequilibrium with respect to surrounding space. It is the dynamic tension between gravity and fusion that enables the star to maintain this seething disequilibrium.
The power of gravitational attraction within a star presses toward total collapse of the star. The power of nuclear fusion, where protons and neutrons fuse together and release energy in the center of the star, aims at expansion: matter is literally pushed outward, the opposite of collapse. If either of these powers comes to dominate, the star’s life ends. The star exists only because these two powers are kept in creative tension for billions of years.
The atoms in a star have a fundamental resistance to being crushed because the electrons of one repel the electrons of the other. If the gravitational attraction is strong enough, the heat that results from this resistance causes atoms to dissociate into free electrons and nuclei.
But gravity does not stop here. The entire process is repeated at the level of the nuclei. Nuclei repel each other, but if the overall gravitational “crushing” is powerful enough, this resistance can also be overcome. The protons and neutrons in adjacent nuclei are brought so close to each other that they can fuse into the stable configuration of a new nucleus. This fusion process converts hydrogen nuclei into helium nuclei, thus releasing enough energy to push the star outward and stave off further collapse.
The star then exists in between extremes. On one side there is gravitational collapse; on the other is thermonuclear fusion and outward pressure. Thus the star exists not in a world of stasis but in a realm of seething disequilibrium. Because the star holds itself in this far-from-equilibrium realm, it is capable of creating helium nuclei out of elementary particles.
This is one of the most amazing discoveries in the history of science. Stars are fiery cauldrons of transformation. Stars are wombs of immense creativity. And one can wonder if these complex interactions that we see in the stars reflect deep patterns of creativity in other domains of the universe. Certainly there are similarities in the human world. Beset with strong emotions of attraction and repulsion, we can, even so, develop emotionally charged bonds that become the foundation for decades of creative action.
There is deep ambiguity threaded throughout that may result not simply in communion but also in collapse. But isn’t this also the nature of the universe—both dangerous and inviting? How do we discover ourselves in forces that are simultaneously fearful and attractive? How do we live amidst shimmering disequilibrium? One thing seems certain: the universe, navigating between extremes, presses ever further into creative intensities.
One of the greatest costs of creativity in the universe is the supernova, an exploding star. The astonishing fact is that many large stars are destined to explode. The energy expended in this event is unrivaled by anything else in the universe. The power of a supernova is equivalent to that of an entire galaxy with a hundred billion shining stars.
Stars do everything possible to avoid such an end. For a star twenty times the size of our Sun, the first challenge comes only ten million years after its birth. Throughout those first ten million years, the star has maintained its state of seething disequilibrium by fusing hydrogen nuclei into helium nuclei in its core. But eventually there is no hydrogen left in the core to fuse. It has all been transformed into helium nuclei. So the outward-pushing energy that came from the fusion processes stops.
When this happens, gravity causes the star to collapse into a smaller space. Without any fusion-derived energy pushing out, the star can press itself ever smaller, but as it does so the core of the star heats up until it reaches the temperature necessary to fuse helium into carbon. Now, once again, the star can settle down into a semistable state, for the new blast of energy in its center is enough to hold back the huge force of gravity. This stable state will continue so long as there is helium to fuse. But once the helium in the core is used up, we have a repeat of the cycle in which the star implodes even further and drives temperatures up until the star reaches the billion-degree temperature necessary to fuse carbon into oxygen. And after this cycle ends, the star fuses the oxygen in the core into silicon, and so on through the heavier elements.
This process comes to an end when there is only iron in the core of the star. Iron does not release any energy when it fuses. When the star comes to a core of iron, the energies that had been pushing out from the center are now gone. There is thus nothing the star can do but implode upon itself.
In a matter of seconds, the entire core of the star becomes a tiny speck. First, all the nuclei are dismantled into their constituent protons and neutrons. Not only has the core of this once brilliant star been reduced to a speck, but the star’s creativity in bringing forth these various elements is erased. And still the contraction continues. The energy of implosion becomes so great that even the free electrons and protons are crushed together to form neutrons. It is at this moment that a great reversal takes place—the supernova explosion. The force of the neutrinos, the elementary particles released during the creation of the neutrons, reverses the entire movement and blasts the star apart. The superconcentrated dot of neutrons now explodes outward with the brilliance of a hundred billion stars. And as it expands, a stupendous new round of nucleosynthesis takes place, creating the nuclei of all the elements of the universe. What had been a dense dot of matter now opens up into hot clouds of magnesium, calcium, phosphorous, carbon, and gold. This womb of intense creativity gives birth to the elements that eventually form our planet and our bodies. Much of the matter of our bodies passed through such an intense and vast explosion.
The supernova is the most spectacular display of destruction and creation in the universe. What are we to make of this, as our very existence—indeed, the very existence of life—depends upon it? Does it suggest that the universe, in order to create a single atom of carbon, requires the destruction of an entire star? Could it be that life is not possible without vast, mysterious, and ongoing transformation?