Chapter 1: The Quest for Cosmic Gold

The formation of gold in the universe has long been attributed to the collisions of neutron stars. However, recent findings suggest that these cataclysmic events are not the sole source of this precious metal.

In 2017, astronomers observed a merger between two neutron stars—extremely dense remnants of massive stars. Initial analyses indicated that such collisions were responsible for creating all elements heavier than iron, including gold. Yet, a new study reveals that these collisions do not produce enough gold to match the concentrations observed throughout the cosmos.

According to astrophysicist Amanda Karakas from Monash University and the ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), “Neutron star mergers did not produce sufficient heavy elements during the early universe, and this remains true even after 14 billion years.”

Section 1.1: The Birth of Elements

Following the Big Bang, the universe primarily consisted of hydrogen and helium, with trace amounts of lithium. All other elements were formed within the nuclear cores of massive stars or during the explosive deaths of supernovae.

Stars like our Sun maintain a delicate balance between gravitational forces pulling inward and the outward pressure generated by thermonuclear reactions at their cores. In approximately four billion years, our Sun will exhaust its hydrogen reserves, leading to its contraction. The increased core pressure will trigger helium fusion, resulting in the Sun expanding into a red giant, potentially engulfing Mercury, Venus, and possibly Earth.

More massive stars undergo multiple cycles of nuclear fusion, producing heavier elements with each cycle. Once iron is formed, any additional fusion requires more energy than is gained, resulting in the star's collapse under gravity and potentially leading to a supernova. These explosions can create elements heavier than iron, including zinc, tin, and gold, leaving behind either a black hole or an ultra-dense neutron star.

Chapter 2: Magnetorotational Supernovae: A New Player?

The first video, "SPACE LAB: Where Did All the Gold in the Universe Come From?" explores the origins of gold in cosmic events and the role of neutron star collisions.

Researchers now propose that magnetorotational supernovae might account for much of the gold observed in the universe. These phenomena occur during the collapse of rapidly spinning massive stars with intense magnetic fields.

During this process, atomic nuclei can absorb neutrons more efficiently than they decay, initiating the creation of heavy elements through the r-process of nuclear fusion. The study suggests that even if a small fraction of stars with masses ranging from 25 to 50 times that of the Sun are magnetorotational, they could significantly contribute to the universe's gold production.

The second video, "How a Cosmic Kilonova Can Create Gold | How the Universe Works," delves into how these cosmic events contribute to the universe's gold supply.

Previously, research indicated that collapsar supernovae—resulting from the collapse of a rapidly rotating massive star—could also produce heavy elements. Interestingly, astronomers have found less gold than anticipated among the stars, alongside a higher-than-expected amount of silver, suggesting that our understanding of element formation may need to be revisited.

The findings of this study are detailed in The Astrophysical Journal. James Maynard, the founder and publisher of The Cosmic Companion, lives in Tucson with his wife, Nicole, and their cat, Max.

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