Nuclear Fusion
Earth and Space

Where have all the elements come from?

Physics Narrative for 11-14 Supporting Physics Teaching

Building atoms in stars

Most of the atoms you are made of were themselves made in stars. Read more about this interesting idea here.

If most of the matter in the universe, at its formation, was hydrogen and helium, where have all the other elements come from?

The estimated age of the universe is 13.7 billion years. The Sun is only about 5000 million years old and was formed out of the remnants of other stars that blew up. Before the formation of the first stars, the matter in the universe consisted only of hydrogen (74 %) and helium (26 %). All of the elements since then have literally been manufactured in stars by nuclear synthesis.

Either lighter nuclei have been sufficiently energetic to undergo nuclear fusion and form heavier nuclei or, alternatively, they have acquired an extra neutron, which has then decayed into a proton, raising the atomic number by one.

What this means is that every one of the heavier elements found in our bodies, beyond hydrogen in water and some of the helium found in our atmosphere, was made in a star millions of years ago.

This idea is captured elegantly by Marcus Chown, a popular science writer:

But if all these examples of our cosmic connectedness fail to impress you, hold up your hand. You are looking at star-dust made flesh. The iron in your blood, the calcium in your bones, the oxygen that fills your lungs each time you take a breath – all were baked in the fiery ovens deep within stars and blown into space when those stars grew old and perished. Every one of us was, quite literally, made in heaven.

Nuclear Fusion
can be analysed using the quantity Binding Energy
can be exhibited by Star
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