The Webb Telescope Has Captured Its First ‘Bulge Fossil Fragment’

Many of the developments shared by astronomers using the James Webb Space Telescope and similar instruments center on trying to understand the history of the galaxy. The latest update from the Webb telescope researchers confirms the existence of a phenomenon known as “bulge fossil fragments” that can offer new insights on the Milky Way’s formation.

The subject of this latest investigation is known as Terzan 5, a region in the center of the galaxy often dubbed “the bulge” that has been challenging for astronomers to study due to the density of stars and presence of dust. Between their observations with the Webb telescope and archival observations taken from the Hubble Space Telescope, the team was able to confirm that Terzan 5 is not a globular star cluster, as it was previously classified. Globular star clusters usually only have one ancient star population. Instead, Terzan 5 has experienced at least four distinct phases of star formation. According to the researchers’ survey, it has two older star populations that were formed 12.5 billion and 4.7 billion years ago. The astronomers also found two more contemporary populations that formed 3.8 billion years ago and 2.5 billion years ago.

“For some reason, this peculiar clump of stars formed separately from the bulge and was not destroyed as the bulge itself formed,” said University of Bologna professor Francesco R. Ferraro, principal investigator of the Webb observations. “Terzan 5 is what we now call a bulge fossil fragment because it resembles the primordial clumps that contributed to the formation of the bulge.”

“Based on observations and in-depth simulations, we think that galaxies in the early Universe had huge discs of gas that fragmented into clumps and formed stars. These clumps migrated to the center of the galaxies, and many merged to form their bulges,” co-author and University of Bologna associate professor Barbara Lanzoni said.

The findings were published in the journal Astronomy & Astrophysics.