06/18/2026
This week, the Hubble Space Telescope and James Webb Space Telescope joined forces to captured this image of a very far away cluster of stars. Based on its distance of 22,000 light years and its direction towards the Sagittarius constellation, Tarzan 5 is located in the Milky Way’s bulge, a dense concentration of stars at the galactic center.
Traditionally classified as a globular cluster due to its dense and spherical structure, astronomers have since reevaluated its nature. Spectral analysis has revealed that the stars within Terzan 5 come from a variety of generations. Some stars are 12.5 billion years old (almost as old as the universe itself) while others are 2.5 billion years old (younger than the Sun) and others sit somewhere in between. This was confirmed by how many metals were found inside them. Stars forge heavier elements while they are alive and spread them across the cosmos when they die to be reintegrated into future stars. So, the more metals, the more recent the generation.
Finding multiple generations of stars within a single cluster is unusual as we typical to find that stars in star clusters tend to all be born together around the same time. Here, the cluster seems to be pick up strays from around the galaxy. Perhaps it is the core of an irregular galaxy half stripped of its previous population in a colossal collision in the dense Milky Way bulge? This has caused astronomers to reclassify Terzan 5 as a fossil fragment. It serves as a microcosm of the Milky Way’s long history.
Image credit: NASA, ESA, CSA, STScI, G. Zullo (University of Bologna), F. R. Ferraro (University of Bologna). Image Processing: A. Pagan (STScI)
