I’m sitting here holding my mother’s wedding ring wondering where the gold came from. I don’t mean which country it came from. I mean where did it come from?
Turns out that I’m holding the remnants of a star. A star that was born and died possibly billions of years ago, perhaps billions of light years away.
In fact it turns out that that’s where I come from too - the calcium in my teeth, the iron in my blood and the sodium in the potato I ate for lunch were all formed in dying stars.
It’s astonishing how recently some of the most mind-bending yet taken-for-granted discoveries were made. For example, around 100 years ago we thought there was only one galaxy - the one we inhabit, which we call the Milky Way. Sure, there were smudges in the sky that were called nebulae, but we thought they were all patches of dust or gas in our galaxy, the Milky Way.
Then in the 1920s, using a technique developed by Henrietta Leavitt, Edwin Hubble worked out that a star he was studying was so far away that it had to be outside our galaxy. In fact it was in what we now know as the Andromeda Galaxy. Anyone in the northern hemisphere with good eyesight can see Andromeda (better with binoculars or a small telescope) - and it’s quite something to think that the photons striking your eye set out on their journey two million years ago.
Suddenly the universe was way bigger than we ever thought it was. Now we know that there are between 100 and 200 billion galaxies in the universe - not just the one we thought until about 100 years ago.
And it wasn’t until even more recently - 1946 - when Fred Hoyle published ‘The Synthesis of the Elements from Hydrogen’ in the Monthly Notices of the Royal Astronomical Society, that we learned how the heavier elements were made.
Here is part of the article’s abstract:
‘Stars that have exhausted their supply of hydrogen in regions where thermonuclear reactions are important enter a collapsing phase. If the mass of the star exceeds Chandrasekhar's limit [i.e. greater than 1.44 times the mass of our sun] collapse will continue until rotational instability occurs. Rotational instability enables the star to throw material off to infinity … The process of rotational instability enables the heavy elements built up in collapsing stars to be distributed in interstellar space’ (emphasis added).
Almost all the elements in the periodic table were created in dying stars. When a star begins to run out of hydrogen towards the end of its life, it expands into a Red Giant (when our sun does this it will swallow up Mercury and Venus). At this point the element carbon is formed. In more massive stars, even heavier elements such as oxygen and iron are created.
The most massive stars end their lives as supernovae, and this is where elements heavier than iron, such as uranium and gold, are formed.
And every atom of gold in the ring I’m holding. Which is billions of years old. In fact I may be holding most of the history of the universe in my hand.