Numerical simulations reveal "dark ages" of star formation in the universe
To observe the formation of the first generation of stars in the universe is very difficult, to understand the formation of the universe's first generation of stars, a team of researchers at the Georgia Institute of Technology's Center for Relativistic Astrophysics recently conducted simulations showing the process of first-generation star formation.
For astronomers, astrophysicists, and cosmologists, it is difficult to discover the first generation of stars that formed in the universe. On the one hand, the current telescope or observatory has very limited observation capabilities, and the farthest object we have ever observed is MACS 1149-JD, a galaxy 13.2 billion light-years away from Earth, found in the Hubble eXtreme Deep Field (XDF) image. On the other hand, it wasn't until about 1 billion years after the Big Bang that the universe began to go through what cosmologists call "Dark Ages." The universe was filled with clouds of gas that blocked out visible and infrared light during this period, so it is difficult for us to observe the universe before that period.
Illustration: The evolutionary history of the universe, with a period called the Universe's "Dark Ages." (Source: Baidu Encyclopedia)
Fortunately, a team of researchers at georgia tech's Center for Relativistic Astrophysics recently conducted numerical simulations that showed the formation of the first generation of stars in the universe. The study was led by Gen Chiaki, a postdoctoral fellow at the center, and Associate Professor John Wise, and was also involved by researchers from the University of Rome, the Rome Observatory, the National Institute of Astrophysics (INAF) and the National Institute of Nuclear Physics (INFN). Their findings have been published in the Monthly Journal of the Royal Astronomical Society.
Based on the life cycle of stars, astrophysicists speculate that the first generation of stars in the universe should be metal-poor stars. About 100 million years after the Big Bang, these stars were formed by a primordial soup containing hydrogen, helium and trace amounts of light metals. This gas would collapse into a star 1,000 times larger than our Sun. These stars have a very short lifespan, and they may only exist for a few million years. During that time, however, the centers of these stars reacted with nuclear reactions to generate many new heavy elements, which dispersed into interstellar matter as the stars collapsed and eventually exploded. Thus, the next generation of stars formed by this interstellar material will contain heavier elements such as carbon, which we call Carbon-Enhanced Metal-Poor stars. Astronomers are now able to understand the elemental composition of these stars, which reflects the results of the nucleosynthesis (fusion) of heavy elements in the first generation of stars.
Illustration: Supernova remnant SNR E0519-69.0 in the Large Magellanic Cloud (Source: Wikipedia)
By studying the formation mechanisms behind these metal-poor stars, scientists can infer what happened during the first generation of stars, the "dark ages" of the universe. As Wise said in a news release at the Advanced Computing Center (TACC) in Texas, "We can't see first-generation stars, so it's important to look at 'living fossils' (second-generation stars) from the early universe." The second generation of stars contains the "fingerprint" of the first generation of stars, that is, the chemical elements released by the first generation of stars in the supernova explosion. Numerical simulations can help us understand exactly what happens in this process. We can use the simulation results to see where the metal elements come from and how the first generation of stars and their supernova explosions affected the second generation of stars. ”
Plot: Density, temperature, and carbon abundance (top) and the formation period of Pop III stars (bottom). (Chiaki et al.)
The team was primarily based on Georgia Tech's PACE cluster for simulations. Meanwhile, the National Science Foundation's (NSF) Extreme Science and Engineering Discovery Environment (XSEDE), TACC's Stampede2 supercomputer, the NSF-funded Frontierera system (the world's fastest academic supercomputer), and the San Diego Supercomputer Center 's ( SDSC ) cluster all support the numerical simulations described above.
With the hashrate support and data storage provided by these computing clusters, the team was able to simulate faint supernovae of the first generation of stars in the universe. The study suggests that carbon-rich metal-poor stars that appear after the first generation of stars are formed by mixing material ejected from supernova explosions of first-generation stars.
Their simulations also suggest that the gas clouds produced by the supernova explosions of the first generation of stars are filled with carbonaceous particles that will form small-mass giga-poor metal stars that may still exist today (these stars are also future research directions). For these stars, Chiaki said: "Compared to the observed carbon-rich metal-rich stars, these stars have very low iron content, about one billionth of the iron abundance of the solar system." However, we can see fragments of gas clouds, which suggests that low-mass stars formed in a state of very low iron abundance. Although such stars have not yet been observed, our research could provide theoretical insights into the formation of the first generation of stars. ”
A new study looks at 52 submillimeter-magnitude galaxies to help us understand the early age of the universe. (University of Nottingham / Omar Almaini)
These studies are constantly evolving as part of the field of study of "galactic archaeology". Just as archaeologists rely on fossil remains and artifacts to understand societies that disappeared centuries ago or thousands of years ago, astronomers are studying ancient stars to learn more about stars that have long since died.
According to Chiaki, the next step in the simulation will not only be limited to the carbon characteristics of ancient stars, but other heavier elements will also be integrated into larger simulations. By doing so, galactic archaeologists hope to learn more about the origin and distribution of life in our universe. "The aim of this study is to understand the origin of elements such as carbon, oxygen, calcium and other elements that are concentrated through the repetitive cycles of matter between the interstellar medium and stars," Chiaki said. Our bodies and the planets we live on are made up of elements such as carbon, oxygen, nitrogen, and calcium, so this study is important to understand the origins of these elements. ”
BY: Matt Williams
FY: Light showers
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