Webb and Hubble Discover Rare 'Bulge Fossil Fragment' in the Milky Way
Image Credit: NASA, ESA, STScI
The history of our galaxy is actively being rewritten. In a joint study released this week, astronomers utilizing both the James Webb Space Telescope and the Hubble Space Telescope confirmed that a dense star cluster known as Terzan 5 is not a standard globular cluster, but rather a remarkably rare "bulge fossil fragment."
A Cosmic Time Capsule
Located deep within the galactic center, Terzan 5 has long been shrouded by thick clouds of interstellar dust. While Hubble provided foundational visible and near-infrared data over a 12-year period, it was the JWST's unprecedented mid-infrared sensitivity that finally pierced the dust veil to reveal the cluster's complex internal structure.
The combined data sets paint a picture of a violently active past:
- Multiple Epochs of Starbirth: The cluster experienced intermittent bursts of star formation, pausing for billions of years before reigniting as it swept up fresh gas during its orbit through the nascent Milky Way.
- Chemical Diversity: Spectroscopic analysis shows massive variations in heavy element abundances among the different stellar generations, indicating that the younger stars formed from the supernova ashes of the older stars.
Reconstructing the Galactic Bulge
This discovery bridges a critical gap in galactic evolution models. Astronomers now believe that billions of years ago, hundreds of massive primordial clumps like Terzan 5 interacted, merged, and dissolved to form the dense, chaotic core of our galaxy.