Everything you need to know about gold and gravitational wave science

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AWhat are neutron stars? They are the super-dense burned-out remnants of dead giant stars that have exploded and collapsed. Their protons and electrons, charged sub-atomic particles, are squeezed together so hard most merge to form inert neutrons. One teaspoonful of neutron star material on Earth would weigh a billion tonnes. How is the gold made? Gold is created from base metal by shunting extra neutrons into the nuclei of lighter “seed” elements such as iron. A pair of colliding neutron stars produces a fireball

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Acalled a “kilonova” in which showers of hot neutrons are rapidly captured by the “seed” nuclei. How much gold? Scientists analysing chemical fingerprints from the radiation produced by the explosion calculated the mass of gold to be greater than the whole of the Earth. What are gravitational waves? They are ripples in space-time predicted by Albert Einstein 100 years ago. On every previous occasion, the gravitational waves were produced by colliding black holes. This time the source was two neutron stars

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AQ Adistorting space-time as they spiralled towards each other and collided. How was the discovery made? First, the gravitational waves were detected by the Ligo (Later Interferometer Gravitational-wave Observatory) facility in the US. It uses laser beams reflected off mirrors to detect them. Two seconds later a Nasa satellite picked up a burst of gamma rays from the explosion. Another gravitational wave detector in Italy helped scientists pinpoint the source in an ageing galaxy, NGC 4993.

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