The James Webb Space Telescope has made a groundbreaking discovery by observing five star clusters in a galaxy that existed just 460 million years after the Big Bang. These clusters could be the first known candidates for protoglobular clusters. The telescope’s infrared capabilities allow it to observe cold objects, distant objects, and objects hidden behind dust, making it an essential tool for studying the early universe.
The discovery was made possible by the gravitational lensing effect, where large clumps of matter in the galaxy act as “magnifying glasses” to magnify the objects behind them. The galactic cluster SPT-CL J0615-5746 acted as a lens, allowing scientists to observe the galaxy Cosmic Gem Arc at 460 million light years after the Big Bang.
The Webb telescope’s observations revealed five compact points along the Cosmic Gem Arc, which appeared duplicated at the other end of the arc. This indicates that the magnification power of the lens cluster was maximum at these points. The region, previously observed by the Hubble Space Telescope in 2018, has properties that suggest it may be a site of reionization.
The data revealed that the star clusters are very dense, with sizes about 3 orders of magnitude larger than typical young star clusters in the local universe. This suggests that they could be precursors to the globular clusters observed in our own Milky Way galaxy.
Globular clusters are clusters of thousands or tens of thousands of stars, gravitationally linked, and scattered throughout the halo of the Milky Way. The discovery of the Gems provides a time scale for the formation of globular clusters and reveals their initial physical properties.
The Gems are also responsible for most of the ultraviolet emission of the galaxy and are a crucial source of reionization of the early universe. The search for these sources, as well as the first stars, is a main objective for the James Webb Space Telescope.
