The recent discovery of hidden nurseries of massive star clusters in nearby galaxies by the ALMA Observatory has revolutionized our understanding of star formation. This groundbreaking research, published in the Monthly Notices of the Royal Astronomical Society, showcases the power of ALMA and the NSF VLA in revealing the intricate details of star cluster formation. By focusing on NGC 3351 and NGC 1097, astronomers have uncovered a cosmic factory where massive star clusters are born and evolve. These circumnuclear rings, located a few hundred to a thousand light-years from the galactic core, are dense, star-forming regions that mimic the conditions of the early universe. What makes this discovery even more fascinating is the ability to distinguish cluster candidates at different stages of their evolution. By tracing cold dust and ionized gas, ALMA has identified young massive cluster candidates, from deeply embedded, dust-shrouded objects to systems that have begun clearing their surroundings. This multi-frequency approach, combined with VLA observations, has allowed astronomers to study the ring of NGC 3351 and NGC 1097 in unprecedented detail, revealing dozens of compact hot spots associated with star cluster formation. The radio data, sensitive to different types of radio emission, provide a comprehensive view of the cluster's story, from the earliest stages to the most advanced ones. The most intriguing aspect is the coexistence of all four stages within the same ring, confirming that massive cluster formation is an ongoing process rather than a single burst. The comparison with James Webb Space Telescope images further validates the findings, as the compact radio sources correspond to star clusters and their surroundings. The most luminous source in NGC 1097 is equivalent to the ionizing power of 1,200 of the hottest, most massive stars, making it one of the most powerful compact star-forming regions. This discovery has profound implications for our understanding of star formation, offering a unique opportunity to study processes that occurred in galaxies billions of years ago. As astronomers continue to explore these circumnuclear rings, we can expect further insights into the assembly of star clusters, their gas conversion efficiency, and the role of stellar feedback in shaping the densest star-forming environments. This research not only advances our knowledge of the present but also provides a window into the past, allowing us to study the conditions that prevailed in the early universe.
