THE CREATION OF THE HEAVIER ELEMENTS
13.4 billion years ago
|Supernova aftermath. The Crab Nebula is the remains of the death of a star that was observed in 1054 A.D.
Credit: Image is used courtesy of NASA/JPL-Caltech
Ancient alchemists dreamed of converting simpler materials into gold (discovering the so-called “philospher’s stone” they thought could accomplish this). Although alchemists were never able to do this, such alchemy happens in the universe all the time. The earliest stars were composed only of the lightest, simplest elements of hydrogen and helium and smaller amounts of deuterium and lithium. It is thought that many of these stars were of enormous size, some hundreds of times larger than our sun. All stars burn through nuclear fusion. Stars smaller than our sun only produce helium from hydrogen in this fusion process. Somewhat larger stars go on to produce heavier elements through fusion, including such as carbon, nitrogen, oxygen, sodium, aluminum, silicon, potassium, calcium and iron. The stellar giants (stars over ten times the mass of our sun) tend to have a relatively short life before they explode (such explosions are called “supernovae”). During this cataclysmic end, these stars producing all of the heaviest elements found in nature (such as nickel, copper, zinc, silver, gold, mercury, lead, and uranium), seeding the universe with clouds (nebulae) of the dust of these heavier elements.
|This is an artist’s impression of SN 2006gy, one of the brightest supernovae ever recorded.
Credit: Image is used courtesy of NASA/CXC/M. Weiss
Our sun is composed mainly of hydrogen and helium, but about two percent of the sun’s composition is from the heavier elements. The presence of these heavier elements indicates that the sun is a second or later generation star, created from the gas and dust of earlier exploded star systems. It is these heavier elements that make up solid planetary bodies like the earth and the complex chemistry that eventually made life possible. It is no exaggeration to say that we are made up of stardust.
HOW DO WE KNOW?
We can now understand the theoretical physics that can create the heavier elements that are created from a star’s catastrophic explosion, and supernovae can occasionally be witnessed in modern times. A famous supernova occurred in 1054 AD, recorded by Chinese astrologers, and was bright enough to be seen in the daytime sky. Another one occurred in 1989, and created a massive expanding cloud of dust and gas called a nebula. Such nebulae are the cosmic nurseries for future stars, and our sun formed in one such nebula 4.6 billion years ago.
WHY SHOULD I CARE?
Our world and our very bodies are made up of reconstituted stardust from these primeval explosions. Without this cosmic alchemy (including stellar fusion and supernovae explosions that produced the heavier elements), there would be no rocks, no water, no atmosphere as we know it, and no organic life.
Crab Nebula: Recent Supernova With A Beating Heart
Wikipedia article on supernovae, concise, in plain language, and with stunning photographs:
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