Humanity’s fascination with gold is heightened by the knowledge that it originates from the stars. This precious metal, coveted for its beauty and unchanging nature, is created through dramatic and violent cosmic events. But how does the universe actually make gold?
Neutron Star Collisions: The most widely accepted theory is that most of the gold in the universe is formed during the collision of neutron stars. These incredibly dense objects are the remnants of massive stars that have previously exploded as supernovae. When two neutron stars spiral into each other, their collision releases a massive burst of energy and a shower of debris. These collisions send gravitational waves rippling through space-time, and also generate heavy elements, including gold. The intense light emitted from these collisions is called a kilonova, and is a key indicator of the creation of heavy elements.
The r-process: The formation of gold during neutron star collisions occurs through the “rapid neutron capture process”, or r-process. This process involves the quick absorption of free neutrons by atomic nuclei, rapidly building up heavy elements like gold. The merger of neutron stars creates a high density of neutrons, which allows existing elements to quickly capture them. Elements such as strontium, thorium, uranium, and gold are formed in a flash, and then dispersed into the universe.
Supernovae: While neutron star collisions are considered the primary source of gold, some gold may also be created during the explosive deaths of massive stars (supernovae) through the r-process. When giant stars exhaust their nuclear fuel, they collapse and rebound in a supernova explosion. This explosion blasts the star’s outer layers into space, and free neutrons penetrate the nuclei of nearby atoms. The elements produced in this process also contribute to the inventory of heavy elements in the universe, including gold.
Gold on Earth: Most of the Earth’s gold sank to the core of the planet due to its density, with an estimated 99 percent of the world’s gold buried deep below the surface. Despite its rarity, gold pervades our lives. From electronics to jewellery, gold is used in many ways, a testament to its enduring allure.
Gold in the Sun: Scientists have calculated that the Sun contains a vast amount of gold, enough to fill Earth’s oceans. However, when compared to the mass of the Sun, this is a tiny amount, with only eight gold atoms for every trillion hydrogen atoms. The heavy elements, including gold, were identified in the Sun’s atmosphere through the use of spectroscopy.
A Gift from the Stars: The next time you see gold, remember that it is not merely a precious metal, but a gift from the stars. Formed in the cataclysmic events of neutron star collisions and supernovae, gold is a tangible reminder that we are all made from the “stuff of stars”.
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