In 2017, astronomers witnessed an explosion 1,000 times brighter than a supernova, which sent gold and platinum cascading into the Universe and caused ripples in space and time itself.
So, where does gold come from? It comes from the stars. To be more specific, it comes from the collision of two neutron stars, which are the dead husks left behind after supernovaeA supernova is a colossal explosion of a star. . When two of these get caught in each other's orbits, they get closer and closer until eventually they crash into each other. This was observed for the very first time in August 2017.
Neutron stars are small compared to most other important objects in space - the two recorded in 2017 were about the size of London - but they are very heavy. A single teaspoonful would weigh about the same as Mount Everest. So, when they slam into each other, the explosion is hot enough to fuse 79 protonsA subatomic particle with a positive electric charge, found in the nucleus of an atom. The number of protons in an atom determines what kind of element it is. with 118 neutronsA subatomic particle with no electric charge, found in the nucleus of an atom., and make a particle of gold. Or, in this case, 236 sextillion tonnes of gold - and also platinum, silver, and other heavy elements which were then spewed into space.
That sounds intense. It was. Scientists have known about the elements of the periodic table for a long time. But, until now, they were unsure what was powerful enough to make the heavy metals that we, earthlings, are fond of turning into jewellery.
Now, they know that - sometimes at least - they come from such an explosion, also known as a kilonova.
Great name. How was this kilonova detected? Buckle up: finding out where gold comes from is just one part of a much bigger story.
In 2015, astronomers detected gravitational waves for the first time. These are tiny ripples in space and time, caused by violent events like the one recorded in August. But over the last two years, scientists have only been able to record the waves coming from two black holes colliding.
We cannot see black holesA region of space where gravity is so strong that nothing can escape from it, including particles and radiation. because, by their nature, they suck light in rather than emit it. But we can see neutron stars. So, when scientists detected the gravitational waves in August, within seconds, powerful telescopes all over the world swivelled around to take a look. "It was the astronomical equivalent of stopping traffic," explained one scientist.
Why is it such a big deal? It was a massive deal when physicists first detected gravitational waves in 2015. Finally, they were able to prove Einstein's theories 100 years after he made them. Earlier this year, three physicists won the Nobel PrizeOne of a set of prizes, laid out in the will of Swedish chemist Alfred Nobel, given each year to people who "have conferred the greatest benefit to humankind". for it. But this time, astronomers were able to combine the gravitational waves with the observations made through telescopes. They could see what happened for the first time.
One scientist said this was like going from "looking at a black-and-white picture [...] to sitting in an IMAX 3D movie".
Another called it a "new era" in astrophysics. Another compared the findings to the Rosetta stoneAn ancient stone containing three translations of the same thing, which helped historians to decipher Egyptian hieroglyphs.. The simple fact is that they have far more data to work with than they did before.
What else did they discover? The kilonova confirmed a lot of things which scientists already suspected, such as gravitational waves travelling at the same speed as light, and short bursts of gamma raysThe most powerful form of electromagnetic radiation. coming from two neutron stars. Then they were able to use the kilonova to measure the rate at which the Universe is expanding. Happily, it fits with their current estimations.
What might they learn next? An answer to what is left in the place of the two neutron stars. The current candidates are a single, much heavier neutron star or a light black hole.
After that, who knows? But scientists predict that they will keep getting better at recording gravitational waves. "It's rather like being an explorer setting foot on a new shore and there's a whole continent ahead of us," said one. "I, for one, cannot wait to get exploring."
Keywords
Supernovae - A supernova is a colossal explosion of a star.
Protons - A subatomic particle with a positive electric charge, found in the nucleus of an atom. The number of protons in an atom determines what kind of element it is.
Neutrons - A subatomic particle with no electric charge, found in the nucleus of an atom.
Black holes - A region of space where gravity is so strong that nothing can escape from it, including particles and radiation.
Nobel prize - One of a set of prizes, laid out in the will of Swedish chemist Alfred Nobel, given each year to people who "have conferred the greatest benefit to humankind".
Rosetta stone - An ancient stone containing three translations of the same thing, which helped historians to decipher Egyptian hieroglyphs.
Gamma rays - The most powerful form of electromagnetic radiation.
The mystery of gold
Glossary
Supernovae - A supernova is a colossal explosion of a star.
Protons - A subatomic particle with a positive electric charge, found in the nucleus of an atom. The number of protons in an atom determines what kind of element it is.
Neutrons - A subatomic particle with no electric charge, found in the nucleus of an atom.
Black holes - A region of space where gravity is so strong that nothing can escape from it, including particles and radiation.
Nobel prize - One of a set of prizes, laid out in the will of Swedish chemist Alfred Nobel, given each year to people who "have conferred the greatest benefit to humankind".
Rosetta stone - An ancient stone containing three translations of the same thing, which helped historians to decipher Egyptian hieroglyphs.
Gamma rays - The most powerful form of electromagnetic radiation.