The James Webb Space Telescope (JWST) has uncovered what might be the earliest star clusters in the universe. JWST spotted these five proto-globular clusters, which are groups of millions of stars bound together by gravity, within the Cosmic Gems arc, a galaxy that came into existence just 460 million years after the Big Bang. The Cosmic Gems arc gets its name from its unique appearance. When viewed from our perspective, the star-studded galaxy resembles a thin crescent due to the powerful gravitational influence of a foreground galaxy, which magnifies and distorts the distant galaxy’s appearance. This galaxy is the most highly magnified region observed within the first 500 million years of our universe, providing astronomers with an unprecedented view into how the early stars shaped galaxies during the era known as cosmic dawn. Cosmic dawn encompasses the first billion years of the universe. Approximately 400 million years after the Big Bang, the Epoch of Reionization commenced, during which light from newly formed stars stripped hydrogen atoms of their electrons, leading to a fundamental shift in the universe’s composition. “The early universe is nothing like we expected,” said study first author, an astronomer at Stockholm University, in an interview with Live Science. “Galaxies are more luminous, they form stars at an astonishing rate, and they do so in massive and dense star clusters. We are developing a new understanding of how early galaxies formed.” The researchers published their findings on June 24 in the journal . As stars form, they release energy and material into the surrounding space, in the form of winds and jets of ionized plasma – a process known as stellar feedback. “To form these 5 star clusters, this tiny galaxy had to do so with very high efficiency,” Adamo explained. “The stellar feedback from the stars in star clusters must have been tremendous.” Scientists discovered the Cosmic Gems arc in 2018 using the . Typically, galaxies from such an early epoch emit light that is too faint for telescopes to detect. However, a phenomenon called gravitational lensing can aid astronomers in observing them. As outlined in Einstein’s theory of general relativity, gravity is the bending and distortion of space-time in the presence of matter and energy. This curved space, in turn, governs the movement of energy and matter. This means that even though light travels in a straight line, it can be bent and magnified by the influence of gravity. In this instance, the galaxy SPT-CL J0615-5746 lies between the Cosmic Gems arc and our solar system, bending and magnifying the early galaxy’s light, making it visible to telescopes. By focusing JWST on this region of curved space, astronomers obtained unprecedented details of the Cosmic Gems arc, resolving the five globular clusters nestled within. They discovered that these clusters were incredibly dense, roughly three orders of magnitude denser than star-forming regions observed closer to Earth. These clusters are among the first ever observed, but it remains unclear whether they are the first to exist, Adamo stated. “In principle, I would expect star formation to occur in a clustered fashion even in quite primordial galaxies,” she added. “But to form [massive] proto globular clusters, the host galaxy needs to be capable of creating and retaining enough mass in gas. So it all depends on how fast primordial galaxies can grow.” To gain further insights into the cosmos’s earliest embers in this region, the researchers will conduct follow-up spectroscopic analysis using JWST. This will enable astronomers to reconstruct the physical properties of the clusters, refine their age estimates, and trace the impact of the clusters’ stars on their surrounding galaxy.
JWST Discovers Earliest Star Clusters, Revolutionizing Our Understanding of Early Universe
