New discovery of the Webb telescope: directly "seeing" galaxy formation

In the May 24, 2024 issue of Science magazine, an article explored the abundance of neutral atomic hydrogen in early galaxies in the universe and its impact on galaxy formation. The research team used near-infrared spectral data from the James Webb Space Telescope JWST to analyze 12 galaxies with redshifts above 8. Through spectral analysis, the researchers found that three of the galaxies showed strong damped Lyman alpha absorption, a feature that indicates that there is a large amount of neutral atomic hydrogen around these galaxies.

These three galaxies are located at redshifts of 8.8, 10.2, and 11.4, corresponding to about 400 million to 600 million years after the Big Bang, when the universe was in the first 3%-4% of its 13.8 billion-year lifetime. This is very early. Their neutral hydrogen column density reaches 10^22 cm^-2, which is an order of magnitude higher than the completely neutral intergalactic medium. This indicates that there is abundant gas in these young galaxies, and this gas is the raw material for galaxy formation.

The article also explored the spectral characteristics of these galaxies, measured their redshift and oxygen abundance, and confirmed that the star formation rate of these galaxies is between 1 and 15 solar masses per year. Through model fitting, the researchers determined that the neutral hydrogen in these galaxies mainly comes from the interior of the galaxy or its neighboring regions, rather than from the intergalactic medium.

The results show that there is a large amount of neutral hydrogen around galaxies in the early universe. This hydrogen gas has a high shielding effect on ionizing photons, thus affecting the galaxy's ionizing radiation escape rate. This discovery is of great significance for understanding the galaxy formation and large-scale ionization process in the early universe.

We know that the formation and evolution of the universe is a grand and complex process that began about 13.8 billion years ago with a process called the Big Bang. The Big Bang theory holds that the universe expanded rapidly from an extremely hot and dense state, then gradually cooled and formed the cosmic structure we see today. In the first few minutes after the Big Bang, elementary particles such as protons, neutrons and electrons began to form, and then these particles combined to form the lightest elements, such as hydrogen and helium.

As the universe continued to expand and cool, gravity began to cause matter to gather, forming the earliest galaxies and stars. These early stars synthesized heavier elements through nuclear fusion reactions and scattered these elements into the surrounding space through supernova explosions at the end of their lives. These heavy elements became the basis for the formation of subsequent stars and planets.

The formation and evolution of galaxies is a key aspect of the evolution of the universe. Galaxies continuously accrete surrounding gas and dust through gravity and continuously evolve through processes such as star formation and galaxy mergers. Star formation activity and supernova explosions in galaxies not only affect the structure and dynamics of the interior of galaxies, but also have an important impact on the intergalactic medium. The intense radiation generated during star formation and the shock waves generated by supernova explosions can heat and ionize the intergalactic medium and even expel some gas from the galaxy.

In addition, dark matter and dark energy also play an important role in the formation and evolution of the universe. Dark matter promotes the aggregation of matter through its gravitational effect, helping to form galaxies and galaxy clusters. Dark energy drives the accelerated expansion of the universe, affecting the large-scale structure and evolution of the universe.

In general, the formation and evolution of the universe is a process from simple to complex, from uniform to structured. Through the study of galaxies, stars and intergalactic media, scientists continue to reveal the details of the evolution of the universe. Many studies in modern astronomy and cosmology focus on understanding these evolutionary processes and the physical mechanisms behind them in order to answer our ultimate questions about the origin and fate of the universe.

This direct "sighting" of galaxy formation is of great significance. It not only verifies theoretical models and enriches our understanding of the early structure of the universe, but also promotes the development of astronomical technology and points the way for future research. This discovery has a far-reaching impact on the scientific community's understanding of the origin and evolution of the universe.

By directly observing the formation of early galaxies, we can better understand the early history of the universe after the Big Bang. Studying the chemical composition of early galaxies and the process of star formation can help us understand the conditions for the formation of life. The elements required for life (such as carbon, nitrogen, oxygen, etc.) were formed in early stars and spread into galaxies through supernova explosions. Understanding these processes helps answer the question of how we evolved life from a lifeless universe. For many people, understanding the origin and evolution of the universe is not only a scientific question, but also a question of philosophy and existential significance. By exploring the origin of the universe and our own origins, we are trying to answer deeper questions about our existence: where do we come from, why do we exist, and what our future will be. These scientific discoveries provide important background and foundation for these philosophical thinking.

This article is a work supported by the Science Popularization China Creation Cultivation Program

Author: Gou Lijun, researcher at the National Astronomical Observatory of the Chinese Academy of Sciences

Reviewer: Sun Zhibin, Researcher, National Space Science Center, Chinese Academy of Sciences

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.