New observations from NASA’s James Webb Space Telescope, combined with archival data from Hubble, have confirmed the existence of a rare “Bulge Fossil Fragment” in the center of the Milky Way. The finding could help astronomers understand how the galaxy’s central region was assembled billions of years ago.
The focus of the study is Terzan 5, a dense object in the Milky Way’s bulge that had long been treated as a globular cluster. Heavy crowding and cosmic dust had made it difficult to study, but the new data show that this object is far more complex than previously thought.
Unlike ordinary globular clusters, which usually contain one old stellar population, Terzan 5 appears to have gone through at least four separate rounds of star formation. The researchers identified two very old populations, formed 12.5 billion years ago and 4.7 billion years ago, and two younger ones, dating to 3.8 billion and 2.5 billion years ago.
Scientists say Terzan 5 seems to have formed separately from the galactic center, yet survived while the Milky Way’s bulge developed around it. Because it resembles the primordial building blocks that helped create galactic centers, it is effectively a fossil from the early universe. The team says early galaxies likely contained massive gas disks that broke into star-forming clumps, which later migrated inward, merged, and formed the dense cores seen today.
