Astronomers using the James Webb Space Telescope have observed a galaxy forming inside-out, just 700 million years after the Big Bang. This discovery offers a unique look at early galaxy growth, with star formation spreading from a dense core to the outer regions.
What is Inside-Out Galaxy Growth?
The term “inside-out growth” refers to the process where star formation in a galaxy begins in the dense core and gradually spreads outward toward the edges. This particular galaxy, detected by the JWST, shows a striking example of such growth. Astronomers observed that the core of the galaxy is densely packed with older stars, while new star formation is happening at a rapid rate in the outskirts. This pattern of growth has been theorized in models, but this discovery marks the first time it has been directly observed so early in the universe’s history.
The galaxy is relatively small—only one-hundredth the size of the Milky Way—but it is surprisingly mature for its age. The discovery challenges earlier models of galaxy formation that suggested galaxies started small and slowly built up over time. The inside-out growth observed in this galaxy offers a new perspective on how early galaxies assembled their structures, suggesting a much more rapid and dynamic process than previously thought.
Observing the Early Universe with JWST
The James Webb Space Telescope is a game-changer for astronomy. Its advanced infrared sensors allow it to observe light from distant galaxies that formed just hundreds of millions of years after the Big Bang. This gives astronomers the ability to look back in time and capture snapshots of the universe during its formative stages. The galaxy displaying inside-out growth is just one example of the new discoveries being made with JWST.
By capturing light emitted by this galaxy at different wavelengths, the JWST provided a wealth of information. Astronomers were able to estimate the ages of the stars in the galaxy, the rate of star formation, and the overall mass of the galaxy. This analysis revealed that while the core of the galaxy contains older stars, the outer regions are undergoing rapid star formation, with the galaxy doubling its stellar mass in these outskirts roughly every 10 million years—a much faster rate than the Milky Way, which doubles its mass every 10 billion years.
The Characteristics of the Galaxy
Despite being a hundred times smaller than the Milky Way, this early galaxy shows signs of remarkable maturity. Its core, densely packed with stars, resembles the dense cores of today’s massive elliptical galaxies. These older stars likely formed first, suggesting that the galaxy’s core is already well developed. What’s even more surprising is that most of the star formation is happening in the outer regions of the galaxy, far from the core. A star-forming “clump” has even been detected beyond the outskirts, suggesting that the galaxy is expanding its mass rapidly.
The JWST’s observations also indicate that the galaxy is rich in gas, which is fueling this rapid star formation. The presence of both older stars in the core and younger stars in the outskirts supports the idea that this galaxy is growing from the inside out. This pattern of growth provides a new framework for understanding how galaxies in the early universe formed and evolved.
Why This Discovery is Important
The significance of this discovery lies not only in the fact that it provides direct evidence for inside-out galaxy growth but also in what it tells us about the conditions of the early universe. For decades, astronomers have used computer models to predict how galaxies formed and evolved.
One of the major questions in astronomy is how galaxies transition from being gas clouds to fully developed, structured systems. The discovery of this inside-out growth pattern gives us a new piece of the puzzle. By studying this galaxy and others like it, scientists can begin to answer questions about the mechanisms driving galaxy growth in the early universe. Was this rapid inside-out growth common among early galaxies, or is this galaxy an outlier? What role did mergers with smaller galaxies play in this process? These are some of the questions that scientists hope to answer as they continue to analyze the data from the JWST.
Moreover, this discovery challenges the traditional view of galaxy evolution. Previous models suggested that galaxies grew slowly over time by accumulating mass through gas accretion and mergers.
Implications for Future Research
The inside-out growth of this galaxy is just the beginning. Researchers are now turning their attention to other galaxies in the same epoch to determine whether this pattern of growth is unique or common. By comparing galaxies at different stages of development, scientists hope to reconstruct the growth cycle of galaxies over cosmic time.
The JWST will continue to play a crucial role in this research. Its ability to observe galaxies in unprecedented detail will allow astronomers to study how different factors, such as gas availability and galaxy mergers, influenced early galaxy growth. This will help build a more comprehensive picture of how galaxies evolved during the universe’s first billion years.
Conclusion
The discovery of inside-out galaxy growth only 700 million years after the Big Bang is a major breakthrough in our understanding of the early universe. Thanks to the James Webb Space Telescope, astronomers now have the ability to observe galaxies at their earliest stages of development, providing critical insights into how galaxies formed and evolved over time. The inside-out growth pattern observed in this galaxy offers a new perspective on galaxy formation, challenging previous models and raising new questions about the forces driving cosmic growth.
The discovery is not just a triumph for astronomers—it’s a reminder that our universe is filled with wonders waiting to be uncovered. Each new observation brings us closer to understanding the cosmos, one galaxy at a time.
