Not so very long ago, astronomers thought that we would never know what stars are made of. Such knowledge would be impossible to obtain, because stars were simply too far away, they reasoned. Today, science and technology allow us to gather stellar light, analyze it and provide “impossible” answers.

We know now that stellar nucleosynthesis, the process whereby stars create successively heavier elements from within themselves, is at work. As gravity slowly collapses a gigantic cloud of primordial gas, largely hydrogen, a protostar forms and proceeds to compact further. The continuing gravitational compaction causes the protostar to heat up more and more until its core reaches a critical temperature of about 15,700,000 C. At this extreme temperature, hydrogen does not exist as intact atoms but as disassociated protons and electrons no longer bound together.

Continuing further, the protons, all positively charged, repel each other. But at over 15 million degrees, they move so fast that their momentum brings them so close together that they come within the fantastically short range of another fundamental force, called the strong nuclear force, which overcomes repulsion and binds them together. This is nuclear fusion, the same process that takes place in a thermonuclear bomb. Hydrogen has been fused into the heavier element helium. The star lights up and shines.

Fusion continues from there, building heavier and heavier (more massive) elements. The total mass of the star determines how far the process goes. Extremely massive stars end their lives in gargantuan supernovae explosions, which generate the heaviest elements, including those that are radioactive. Supernovae explosions distribute all of the star-manufactured elements into the interstellar medium.

All of this atomic physics talk is intended to underscore an essential conclusion: Stars manufacture all elements past the first three on the famous periodic chart, so-called Big Bang primordial elements, all the way up to massive elements, including and beyond those necessary for life as we know it. When you look up at night, you are seeing factories called stars, without which the constituents for our entire natural world would not exist, including all those needed for life.

— Kent Fairfield is a volunteer with Pine Mountain Observatory and a lifelong amateur astronomer. He can be reached at kent.fairfield@gmail.com. Other PMO volunteers also contributed to this article.