Webb, Hubble Reclassify 22,000-Light-Year Terzan 5 as Bulge Fossil Fragment
Updated
Updated · European Space Agency · Jun 16
Webb, Hubble Reclassify 22,000-Light-Year Terzan 5 as Bulge Fossil Fragment
3 articles · Updated · European Space Agency · Jun 16
Summary
Terzan 5 has been reclassified from a globular cluster to a bulge fossil fragment after Webb and Hubble data showed it contains four distinct stellar populations.
Two newly identified populations formed 3.8 billion and 2.5 billion years ago, while the telescopes also pinned the older groups to 12.5 billion and 4.7 billion years with unprecedented precision.
That age spread, along with differing iron abundances, marks Terzan 5 as a self-enriching stellar system rather than the simpler single-population structure expected of a globular cluster.
About 22,000 light-years away in Sagittarius, Terzan 5 packs roughly 2 million solar masses into a region only a few tens of light-years across, making it one of the Milky Way's densest cluster-like systems.
The finding gives astronomers a rare fossil record of how the Milky Way's central bulge formed in its dust-choked, tightly crowded core.
If this star cluster was misidentified for decades, how many more cosmic fossils are hiding in plain sight across our galaxy?
A 'fossil' from our galaxy's birth has been found. What does this ancient relic reveal about the Milky Way’s chaotic construction?
From Globular Cluster to Bulge Fossil Fragment: How Terzan 5’s Multi-Generational Stars Rewrite Galactic History
Overview
Terzan 5, once thought to be a typical globular cluster hidden in the Milky Way’s bulge, has been reclassified as a 'bulge fossil fragment' after a major study using JWST and HST data. This discovery marks a big change in our understanding, showing that Terzan 5 is not a simple cluster of old stars but a rare survivor with a complex star formation history. Unlike normal globular clusters, which have just one ancient generation of stars, Terzan 5 contains multiple generations, revealing its unique role as a relic from the galaxy’s early days.