The origins of heavy elements such as gold have been one of the biggest mysteries of astrophysics. A study has now provided a clue about the precious metal’s cosmic origins.
Scientists have found that explosions in highly magnetised neutron stars, called magnetars, could have created gold in the universe.
Here is more about the study:
What is the latest discovery about the origins of gold?
Analysis of archival data from space missions shows that a large amount of heavy metals, including gold, come from giant flares from magnetars, according to a study published in The Astrophysical Journal Letters on April 29.
Anirudh Patel, a doctoral student at the Department of Physics at Columbia University in New York, led the study, which used 20-year-old archival telescope data from NASA and European Space Agency telescopes to investigate how heavy elements such as iron and gold were created and distributed throughout the universe.
“It’s a pretty fundamental question in terms of the origin of complex matter in the universe,” Patel was quoted as saying in an article on the NASA website. “It’s a fun puzzle that hasn’t actually been solved.”
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The authors estimated that magnetar giant flares could contribute up to 10 percent of the overall abundance of elements in the galaxy that are heavier than iron.
Co-authors of the study are affiliated with Columbia University, Charles University in the Czech Republic, Louisiana State University, the Flatiron Institute in New York and Ohio State University.
What is a magnetar, and how could gold be formed on it?
A magnetar is a type of neutron star that is highly magnetised, which means its magnetic field is extremely powerful. When a massive star explodes, it leaves a very dense, collapsed core behind, which is called a neutron star.
Astronomers theorise that the first magnetars were formed after the first stars about 13.6 billion years ago, according to study coauthor Eric Burns, assistant professor and astrophysicist at Louisiana State University in Baton Rouge. The Big Bang created the universe 13.8 billion years ago.
On rare occasions, magnetars can release high-energy radiation by undergoing a “starquake”. Like an earthquake, a starquake can fracture the magnetar’s crust. Sometimes, magnetar starquakes bring with them a magnetar giant flare, a rare explosive event that releases gamma rays.
The researchers found that magnetars release material during giant flares. However, they do not yet have a physical explanation for this.
The researchers speculated about whether magnetar giant flares formed gold through the rapid process of neutrons forging lighter atomic nuclei into heavier ones. An element’s identity is defined by the number of protons it has. However, if an atom acquires an extra neutron, it can undergo nuclear decay, which can turn a neutron into a proton.
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A changed number of protons can change the element’s identity. Neutron stars have an extremely high density of neutrons. If a neutron star is disrupted, singular atoms can quickly capture a number of neutrons and undergo multiple decays. This leads to the formation of much heavier elements like uranium.
Before this study, the creation of gold was attributed only to neutron star collisions, or kilonovas. When astronomers observed a neutron star collision in 2017 through telescopes, they found the collision could create heavy elements such as gold, platinum and lead. However, these collisions are believed to have happened relatively later in the history of the universe, in the past several billion years.
However, the archival telescopic data, which was previously indecipherable, showed that magnetar giant flares formed much earlier. Hence, the study indicates that the first gold could have been made from magnetar giant flares.
What’s next?
NASA has an upcoming mission that can follow up on these results. The Compton Spectrometer and Imager (COSI) is a gamma-ray telescope that is expected to launch in 2027.
COSI will study energetic phenomena in the Milky Way and beyond, such as magnetar giant flares. According to the NASA website, COSI could identify individual elements created in the giant flares, helping to form a better understanding of the origin of the elements.