The Birth of Atoms

Your body contains trillions of atoms, of many different elements. There are atoms of hydrogen and oxygen, carbon and nitrogen,...but your body also contains many atoms of calcium, nickel, potassium, iron...even gold!
In all, there are 92 different types of atoms, most of which can be found in the molecules that make up the tissues of your body.
Since we know that when the universe formed, the only elements around were hydrogen and helium, where did all these other types of atoms come from?
The answer is quite startling...all of the atoms in your body, other than helium and hydrogen, were manufactured in the center of a supernova...a star that once existed, but destroyed itself in a gigantic explosion!

To understand how this is possible, we need to look at what atoms are. The simplest atom is hydrogen, which contains a nucleus composed of one proton, circled by one moving electron. The next simplest atom, helium, has a nucleus with 2 protons, and is circled by 2 electrons.
The biggest naturally occurring atom is uranium, with 92 protons, and 92 electrons.
(For simplicity, we will ignore the fact that these atoms also contain neutrons in their nuclei.)





It is possible for small atoms to combine to form bigger ones...but only under intense heat and pressure...the millions of degrees found in the center of a star. This process is called nuclear fusion.



Large stars will be so hot in their interior that hydrogen atoms are forced together to form helium atoms, helium atoms are forced together to form still larger atoms,...and so on. Eventually, large stars will contain in their interior, shells of many different heavier atoms, some as big as iron (57 protons).
If the star is large enough, when it runs out of fuel it will collapse in on itself. The relatively cooler outer layers hit the incredibly hot interior, and a massive explosion occurs, called a supernova. Stars that do this don't live very long...while a smaller star like our sun may burn for tens of billions of years, a massive star that is destined to become a supernova may burn out and explode in a matter of a few million years...a ten-thousandth of the lifetime of our sun.
During this explosion, temperatures rise once again; coupled with intense pressure, this is enough energy to force larger atoms to combine, creating all of the heavier elements from iron to uranium!
This explosion is so large that it propels the contents of the star out into space...including all the heavy elements it has made. Vast clouds of atoms of all types remain, where once there was a star.

We know that at the beginning of the universe, there was only hydrogen and helium. Massive stars formed from these gases, burned out in a few million years, and spewed the heavy elements they created into space around them.
This process has occurred over and over since the universe began some 17 billion years ago. We can observe it still happening today, in our large telescopes.
When our star (the sun) and its family of planets formed from interstellar gases some 5 billion years ago, those gases were already well seeded with heavy elements formed in supernovas that occurred in our interstellar neighborhood in the previous 12 billion years. All of the heavier elements that went into forming the earth, the ground, the biosphere,... everything... came from this interstellar gas cloud. And so did all the elements in your body!

If you would like to learn more astronomy & astrophysics, visit 'We Are Not Alone'.