Scientists have established how heavy elements such as gold and uranium trace their beginnings back to the collision of massive neutron stars.

There were only two phenomena which scientists thought were capable of producing the extraordinary gravitational forces needed to forge the heaviest elements in the universe.

A supernova, when a massive star collapses in its old age and explodes under its own weight, was considered possible.

The other option was the merger of neutron stars – tiny stars of incredible mass – which would result in an enormous spray of stellar debris.

Astrophysicists have now proved the latter after a gravitational wave signal, named GW170817, was detected at 1.41pm UK time on 17 August.

Image:
An artist’s impression of a neutron star

So catastrophically powerful was the collision between two neutron stars – measuring about 12km in diameter each – that it made ripples in the very fabric of the universe, leading to the fifth detection of gravitational waves on Earth.

Scientists “heard” the collision by measuring vibrations in space-time and used telescopes to monitor the radiation from the collision, which they called a “kilonova”.

As telescopes – both on Earth and on satellites – turned towards the collision, which took place 130 million years ago, they were able to analyse the light to see what elements were being produced.

Astronomers have spoken of the discovery that kilonova is responsible for creating the majority of elements such as gold as opening a “new chapter in astrophysics”.

Dr Joe Lyman, from the University of Warwick, said: “The exquisite observations obtained in a few days showed we were observing a kilonova, an object whose light is powered by extreme nuclear reactions.

“This tells us that the heavy elements, like the gold or platinum in jewellery, are the cinders, forged in the billion degree remnants of a merging neutron star.”

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Image:
Heavy elements such as gold were created in the neutron star collision

Dr Samantha Oates, also from the University of Warwick, said: “This discovery has answered three questions that astronomers have been puzzling for decades.

“What happens when neutron stars merge? What causes the short duration gamma-ray bursts? Where are the heavy elements, like gold, made?

“In the space of about a week all three of these mysteries were solved.”

Professor Laura Cadonati, from Georgia Institute of Technology, and the Laser Interferometer Gravitational-Wave Observatory (Ligo), which first observed gravitational waves in 2015, said: “This detection has genuinely opened the doors to a new way of doing astrophysics.

“I expect it will be remembered as one of the most studied astrophysical events in history.”

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