A newly recognised type of stellar remnant
An international team of researchers using the James Webb Space Telescope (JWST) and the Hubble Space Telescope (HST) has identified a distinct class of objects in the Milky Way’s central bulge. These objects, termed bulge fossil fragments, appear to be relics from the earliest stages of our galaxy’s formation.
Terzan 5: the prototype object
The focus of the study is the stellar system Terzan 5, previously classified as a typical globular cluster. New observations reveal a far more complex structure, containing multiple stellar populations with differing ages and metallicities, indicating a multi‑phase formation history.
Observations with JWST and HST
High‑resolution infrared and optical imaging allowed precise determination of the chemical composition and ages of Terzan 5’s stars. The data show that the system formed within the first few billion years after the Big Bang and has remained largely unchanged, making it a genuine fossil record of galactic assembly.
Implications for Milky Way formation
The identification of a new object class provides fresh insight into how the Milky Way’s central region assembled. Unlike ordinary globular clusters, which generally host a single stellar population, bulge fossil fragments contain several generations of stars formed during brief, intense star‑burst episodes.
Future work
- Additional JWST observations will search for similar fragments throughout the bulge.
- Comparative studies with other galaxies may reveal universal aspects of galaxy formation.
- The findings highlight the collaborative role of NASA, ESA and CSA in probing galactic structure.