The hundreds of gold-rich stars discovered in our Milky Way galaxy may have come from smaller galaxies that merged 10 billion years ago, according to new simulations by a supercomputer.
Using the ATERUI II supercomputer in the Center for Computational Astrophysics at the National Astronomical Observatory of Japan, scientists at Tohoku University and the University of Notre Dame developed new simulations of galaxy formation with the highest resolution yet.
The paper was published this week in the Monthly Notices of the Royal Astronomical Society.
The simulation tracked the formation of a virtual Milky-Way-like galaxy from the Big Bang to the present to allow scientists to see how new materials released by old stars are absorbed into new stars.
The elements around us on Earth—from carbon and oxygen to silicon and gold produced by thermonuclear reactions inside ancient stars. These elements are spread around the universe when stars explode.
“The gold-rich stars today tell us the history of the Milky Way,” said Yutaka Hirai from Tohoku University. “These ancient galaxies are the building blocks of the Milky Way. Our findings mean many of the gold-rich stars we see today are the fossil records of the Milky Way’s formation over 10 billion years ago.”
The simulation, which lasted for several months, made it possible for the first time to the scientists to watch the formation of gold-rich stars in the Milky Way.
It revealed that most of the gold-rich stars formed over 10 billion years ago in small galaxies, which later merged to form the Milky Way. Elements heavier than iron—such as gold and platinum—come from the kind of neutron star mergers (when the cores of two dying stars collide) that are thought to be common in small galaxies.
Although the simulations are merely a prediction of what could have happened, the predicted abundance of gold-enriched stars in the present day Milky Way matches what astronomers can now observe.
Over the past five years hundreds of gold-rich stars have been detected. Back in May 2022 scientists used the Hubble Space Telescope to discover 65 elements—including gold—in a star called HD 222925, a record for any object beyond our solar system.
Exactly how, why and when elements are produced is the focus of a lot of advanced research. Last week the European Union announced an award of €11.3 million to the HEAVYMETAL (How Neutron Star Mergers make Heavy Elements) research project, which aims to investigate the synthesis of chemical elements in neutron star mergers.
When stars about eight times the mass of our Sun exhaust their fuel they collapse and blow apart in supernova explosions, eventually becoming either a neutron star or a black hole.
Wishing you clear skies and wide eyes.