'Inside-Out' Galaxy Growth Observed In Early Universe By James Webb Space Telescope
Utilizing the NASA/ESA James Webb Space Telescope (JWST astronomers have made groundbreaking observations of a galaxy expanding from its core outwards—a phenomenon known as 'inside-out' growth. This galaxy, which emerged merely 700 million years following the Big Bang, presents characteristics unexpectedly mature for its age, suggesting a rapid expansion akin to a bustling metropolis, with a densely packed center and less dense outskirts where star formation is picking up speed. This marks the most ancient evidence of such galactic growth, showcasing the advanced capabilities of the JWST in peering back into the early epochs of the universe.
The galaxy in question, though significantly smaller than the Milky Way—being one hundred times smaller—displays a surprising level of maturity. Its core is densely packed with stars, resembling the populous center of a large city, while its outskirts, or 'suburbs,' experience a faster pace of star formation, indicating a sprawling growth. This acceleration in the galaxy's expansion and star formation at its edges has now been observed directly, thanks to the JWST, confirming theories that have long been predicted through computational models.
Dr. Sandro Tacchella, co-lead author from the University of Cambridge's Cavendish Laboratory, highlighted the significance of this discovery, stating, "The question of how galaxies evolve over cosmic time is an important one in astrophysics." The JWST's ability to gather observational data from the universe's first billion years opens new avenues for exploring how galaxies transition from gas clouds to their present complex structures. This insight was further detailed in the findings published in the journal Nature Astronomy, underscoring the telescope's role in expanding our understanding of galactic development across cosmic history.
The observed galaxy is not only forming stars at a rapid rate in its outskirts but also contains a star-forming 'clump' located even further from the core. This activity indicates a significant increase in star formation toward the galaxy's edges, suggesting a growth pattern that aligns with theoretical predictions. Such a pattern, now observable with the JWST, allows astronomers, including Ph.D. student and co-author William Baker from the Cavendish, to validate theoretical models with empirical evidence, likening it to "being able to check your homework."
Galaxies grow through mechanisms like gas accretion to form new stars or by merging with other galaxies. The JWST's observations provide insights into these processes in the galaxy's early stages, offering a glimpse into the dynamics at play. Tacchella compares the galaxy's growth to a spinning figure skater, gathering momentum as it pulls in gas from further afield, eventually adopting spiral or disk shapes commonly observed in the cosmos.
Insights into Star Formation and Galactic Structure
The study revealed that this galaxy's core is as densely packed as those of massive elliptical galaxies today, which have a thousand times more stars. By analyzing the light at different wavelengths, the researchers estimated the stellar mass and star formation rate, uncovering a rapid doubling of stellar mass in the galaxy's outskirts approximately every 10 million years—a stark contrast to the Milky Way, which doubles its mass every 10 billion years.
The presence of older stars in the core and very active star formation in the surrounding disk underscores the galaxy's ample gas reserves, necessary for new star formation. This abundance may reflect the unique conditions of the early universe, hinting at a period when galaxies were rich in the raw materials needed for star birth.
Tacchella emphasizes the need for further research, stating, "Of course, this is only one galaxy, so we need to know what other galaxies at the time were doing." By examining data from additional galaxies, researchers hope to piece together the galactic growth cycle, shedding light on how galaxies reached their current sizes and structures. This endeavor aims to reconstruct the evolutionary paths of galaxies across cosmic time, potentially providing a comprehensive overview of their development from the early universe to the present day.
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