How Gravitational Waves Pointed Us to the Origin of Gold

Based on Brian Metzger Research's Research:

The first sighting of the neutron star merger presented another possibility of how heavy metals were produced in the universe. Previously, many theorized that supernovas produced these metals. However, this was not an efficient way of producing heavy metals. Since these metals are very dense and require more protons, they also require a lot more energy to produce. Stars are efficient at producing lighter elements, turning hydrogen into iron, but fusing more than 26 protons into iron becomes more of a challenge.

When observing the binary neutron star merger for the first time, flashes of light were seen, containing signatures of heavy metals. Data collection showed that the merger ejected gold 10 times Earth’s mass, platinum 50 times Earth’s mass, and other metals such as uranium. This presented an alternate and more efficient way to understand how many of the universe's heavy metals were formed.

From observing this phenomenon, astronomers also discovered more information regarding gravitational waves. In 2015, astronomers detected gravitational waves directly from merging black holes through LIGO. According to Einstein's theory of relativity, orbiting bodies emit gravitational waves, causing the orbit to shrink. As a result, the strength of the waves grows in frequency and amplitude, producing a chirp signal. The neutron star merger/black hole exhibited Einstein’s hypothesis and disproved many modified gravity theories.

These modified gravity theories proposed that light waves and gravitational waves would arrive at different times. However, the neutron star event disproved many of these theories. (Sutter) Astronomers studied the gravitational wave signal and gamma-ray burst signal from the neutron stars. Instead of the gravitational waves and light waves arriving at different times, LIGO picked up the gravitational waves and light from two colliding neutron stars arriving within 2 seconds of each other. Since both sources were 130 million light-years away, the difference was only a 1-in-a-billion-time difference, essentially proving the two signals arrived at the same time. (Sutter)

It’s incredible how telescopes and interferometers are able to detect gravitational waves and study light to precisely identify different types of elements/materials hundreds of millions of light-years away.

What I find even more fascinating is how astronomers were able to identify metals and, specifically, the type of metals (silicon, gold, platinum, etc.) in the neutron star merger. But what I found even more interesting is how these events could turn heavy elements, such as iron, into gold. When a gas transforms into another gas, it seems plausible because gas is odorless and normally invisible. However, when I try to conceptualize metals transitioning into other metals, it’s harder to grasp. Metals have different textures, colors, etc., so it's difficult to imagine iron turning into gold or platinum.

Before reading this article and delving more into the science of astrophysics, I didn’t really think about the process of how elements came to exist. Like previous theories, I always assumed elements were produced from exploding stars, like supernovas. Specifically, I thought elements couldn’t shift into other elements and were static.

Hollywood has interesting depictions of radioactive decay and elements "transforming" into other elements. They often associate turning iron into gold with alchemy and magic. Alchemy is not even considered within the science fiction realm—it’s magical, unachievable, mysterious, and impossible. Learning the origins of elements and how they are made is quite interesting. With this discovery, I would be very interested to read science fiction novels that encapsulate this phenomenon.

Citations

Sutter, P. (2021, September 27). How neutron star collisions flooded Earth with gold and other

precious metals. Space.com. Retrieved December 3, 2022, from

https://www.space.com/neutron-star-collisions-gave-earth-precious-metals