It may come as a surprise to many people but gold, although recovered from the earth, is intimately linked to outer space in numerous ways.
Gold (and many other of the ‘heavier’ elements) first came into existence thanks to enormous explosions which regularly pepper the Universe. Until recently, most scientific evidence pointed to supernovas as the events which provided enough heat and pressure to form the heavier elements such as gold (a supernova is a large explosion which takes place at the end of a star’s life cycle). More recent observations suggest the collision of neutron stars as the source of gold’s formation.
It is somewhat ironic that after its origins in outer space, humans then spent a considerable amount of time producing gold and sending some of it back into space. The reason…? Gold’s physical properties give it a number of advantages over other materials, especially in harsh environments such as those found in space.
One of NASA’s current flagship programs is the James Webb Space Telescope (JWST), which is destined to be the successor of the Hubble Telescope. The JWST has 18 enormous primary mirrors made of the light metal beryllium, each of which is coated with a 100 nanometre-thin coating of pure gold. This coating improves the mirror’s reflection of infrared light (figure 1).
Another prominent example of gold’s unique reflective capability is its use within the visor of a space helmet. The visor itself is coated with a thin layer of gold that filters out the sun’s harmful rays, protecting the astronaut’s face and eyes.
However, the gold used in space is not always so obvious. Because of its reliability, significant quantities of the metal are used in the electronic systems of both shuttles and space stations. NASA has also reported using gold to improve the performance of fuel cells used in space. Fuel cells are an absolutely critical power source – they combine hydrogen and oxygen to produce electricity, and the only by-product they create in the process is water. These clean energy sources provide all of the electrical power for the shuttle orbiter and drinking water for the astronauts.
Finally, gold is to be used in important experiments performed by astronauts. The European Space Agency launched the LISA Pathfinder in late 2015 with a view to identifying gravitational waves, which they describe as ‘dents in space-time.’ They hope to achieve this by suspending two identical cubes of metal in a near-perfect gravitational free-fall and measuring their motion. The metal cubes are made of gold and platinum.
Gold is a critically important material with many surprising uses, both on and off Earth, and its unique properties will continue to help scientists understand our Universe for years to come.