Gold Has Cosmic Origins? Scientist Explains Why NASA James Webb Space Telescope Has Gold-Coated Mirrors

Gold, which is one of the heaviest elements in the periodic table, is believed to be synthesised during a very special explosion process in the cosmos

NASA’s James Webb Space Telescope | Photo: NASA

New Delhi: Did you know the James Webb Space Telescope (JWST), scheduled to be launched on December 18, has mirrors coated with gold?

A little more than 48 grams of gold have been used in the mirrors of the orbiting infrared laboratory, which will extend the discoveries of the Hubble Space Telescope. 

But why has gold been used for the mirrors?

Webb's mirrors are covered in a microscopically thin layer of gold to optimise the mirrors for reflecting infrared light, according to NASA. Gold reflects up to 99 per cent of all the infrared light it encounters. Also, gold is one of the most unreactive metals, and is extremely durable to oxidise and decay in space. 

Gold is believed to have cosmic origins, which has been a matter of debate. In a recent video by NASA's Goddard Space Flight Center, however, Dr Mansi Kasliwal, Professor of Astronomy at California Institute of Technology, has now explained the cosmic origins of Gold. 

Gold Comes From Special Explosion Events In The Cosmos

Gold is one of the heaviest elements in the periodic table, and a gold atom has 197 neutrons and protons, Kasliwal explains in the video. Until a few years ago, scientists had no idea where gold is made in the universe, she says.

For many years, scientists debated what energetic event could lead to the formation of heavy elements. They tried to find whether the power of a supernova is enough to synthesise heavy elements. 

Kasliwal explains that a very special explosion process in the cosmos is necessary to synthesise heavy elements like gold. One such process is the r-process.

What is an r-process?

An r-process, also known as the Rapid Neutron Capture Process, is responsible for the creation of approximately half of the atomic nuclei heavier than iron, or "heavy elements". 

In the video, it is explained that the r-process happens in a couple of seconds. On August 17, 2017, two neutron stars had merged, which is when the astronomers at Caltech saw the hallmark infrared signature of an r-process for the very first time, Kasliwal says.

The binary neutron star merger was the source of a gravitational wave signal that lasted less than 100 seconds, and detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) on Earth. The neutron star merger that occurred in 2017 is an important event because it was the only time scientists witnessed and measured the r-process in action. The r-process was theoretical before the merger.

How Does An r-process Form Gold?

The two neutron stars were spiralling towards each other, and merging to give birth to a black hole. This is when astronomers thought they had witnessed the synthesis of gold for the first time, Kasliwal says in the video. There is an abundant supply of free neutrons in the vicinity of neutron stars; so, when the neutrons are flying out, they are able to bind to each other and undergo the rapid capture process. The rapid capture results in the creation of a large number of heavy elements, including gold, she explains. 

Gold has been there on Earth since the formation of the planet, and has been floating around in the cosmos ever since the formation of the universe. The precious element, which was forged in the death of stars, and is now a part of the Webb Telescope, will be used investigate to the dawn of the universe.