Webb Telescope Captures Bulge Fossil Fragment, Offering New Evidence on Galaxy Formation

According to a report by Engadget, the James Webb Space Telescope (JWST) has successfully conducted detailed observations of the galactic center region known as “Terzan 5.” The findings confirm that this celestial body, previously classified as a globular cluster, is instead a “bulge fossil fragment,” a remnant from the early stages of galaxy formation. This groundbreaking research has been published in the astronomy journal Astronomy & Astrophysics.

At the center of a galaxy lies a dense, elliptical region known as the “bulge.” The bulge of the Milky Way is a densely packed area of stars, where the presence of dust has long made observations with traditional optical telescopes challenging. By combining JWST’s infrared capabilities with archival data from the Hubble Space Telescope, scientists have unraveled the detailed composition and age of the stars in Terzan 5.

Discovery Overturns Globular Cluster Theory

Terzan 5 was traditionally regarded as a type of globular cluster, which is generally understood to consist of a single population of ancient stars. However, recent observations reveal that Terzan 5 contains at least four distinct star formation periods.

According to the research team, Terzan 5 hosts two ancient star populations formed approximately 12.5 billion years ago and 4.7 billion years ago, alongside younger star populations formed around 3.8 billion years ago and 2.5 billion years ago. This multi-generational structure is incompatible with existing models of globular cluster formation.

Professor Francesco R. Ferraro from the University of Bologna stated, “For some reason, this unique stellar cluster separated from the bulge during its formation and remained intact even as the bulge itself was forming. Terzan 5 is similar to the primordial fragments that contributed to bulge formation. We call it a bulge fossil fragment.”

Aligning with Galaxy Formation Theories

Associate Professor Barbara Lanzoni, also from the University of Bologna, explained how this discovery aligns with theoretical simulations of galaxy formation. “Based on observations and detailed simulations, early galaxies in the universe were surrounded by massive gas disks that fragmented into clumps, which then formed stars. These clumps migrated toward the galactic center, where many merged to form the bulge.”

The findings from this study provide direct evidence supporting this “clump merger” model. As a primordial fragment that avoided merging, Terzan 5 serves as a fossil-like remnant, preserving insights into the early stages of galaxy formation.

How Webb Telescope Enabled the Discovery

This breakthrough was made possible by the JWST’s advanced infrared capabilities. The densely packed galactic center is obscured by dust, making it difficult to observe in visible light. However, infrared wavelengths can penetrate this dust, allowing scientists to observe the stars hidden within. Using the telescope’s Mid-Infrared Instrument (MIRI) and Near-Infrared Camera (NIRCam), the researchers identified differences in the stars’ ages and chemical compositions that were previously undetectable with other telescopes.

By combining JWST’s data with archival observations from the Hubble Space Telescope, the team was able to track star formation activities across a broader timeline. The complementary capabilities of these two space telescopes provided unprecedented resolution and depth that a single instrument could not achieve on its own.

Editorial Opinion

This discovery underscores how the James Webb Space Telescope, just a few years after its launch, is already reshaping the paradigms of fundamental astronomy. By successfully observing a high-density, challenging region at the heart of our galaxy and challenging the traditional classification of globular clusters, this breakthrough demonstrates the profound impact of advancing observational technology on scientific theories.

In the coming months, similar “bulge fossil fragments” are likely to be identified in other galaxies, prompting revisions to the initial conditions of galaxy formation simulations. From a long-term perspective, this discovery reaffirms the JWST’s pivotal role in unraveling the mysteries of galactic evolution. While the telescope often garners attention for its observations of exoplanets and new stars, its contributions to foundational research on the history of the Milky Way are equally significant. With further advancements in infrared observation and stellar age determination techniques, scientists will be better equipped to construct more precise models of galaxy formation and the growth processes of bulges and disks.

From the editorial team’s viewpoint, this finding highlights the importance of fundamental science. While large-scale projects like the JWST are often discussed in terms of their applications or commercial implications, foundational research into the universe’s basic principles frequently drives advancements in observational technologies and data analysis methods. The study of “fossils” hidden in galactic centers may, in turn, lead to unexpected innovations in machine learning for image analysis and infrared sensor technologies, offering broader implications for technology as a whole.

References

• The Webb telescope has captured its first ‘bulge fossil fragment’ - Engadget — Published on June 16, 2026
• [Astronomy & Astrophysics Published Paper — Refer to relevant issue (source information)]