Astronomers Discover Ancient Star Factories in Distant Galaxies

Astronomers from the University of Arizona have unveiled new findings that reveal massive, dense star factories in numerous galaxies across the local universe, marking a significant advancement in our understanding of cosmic evolution. These star-forming regions, known as luminous and ultra-luminous infrared galaxies (LIRGs and ULIRGs), differ markedly from the familiar spiral structures like our Milky Way, offering a glimpse into the universe's early developmental stages.

The research, presented by Sean Linden, a research associate at the University of Arizona's Steward Observatory, took place during the 246th meeting of the American Astronomical Society on June 11, 2025. According to Linden, there are approximately 202 known LIRGs and ULIRGs within 400 megaparsecs (1.3 billion light-years) from Earth. "These galaxies are very clumpy, very different from the beautiful spiral galaxies that we see now, such as the Milky Way," he stated, emphasizing that these clumps are crucial building blocks in the formation of galaxies during the universe's infancy.

LIRGs and ULIRGs are characterized by their ongoing mergers with other galaxies, which results in unique features such as multiple galactic nuclei and extended tails. Unlike evolved galaxies that typically contain fewer star-forming clumps, these ancient star factories exhibit dense regions teeming with newborn stars.

The Great Observatories All-sky LIRG Survey (GOALS) is a comprehensive study incorporating imaging and spectroscopic data from NASA's Spitzer, Hubble, Chandra, and GALEX observatories. This survey aims to provide the most complete census of luminous infrared-selected galaxies in the local universe. Current observations from the James Webb Space Telescope (JWST) have enabled astronomers to penetrate thick dust clouds that previously obscured these significant cosmic features.

The implications of this research are profound. By analyzing the star-forming clumps within these galaxies, researchers can better understand the processes that shaped galaxies throughout cosmic time. Linden remarked, "In a sense, you look at the local universe, and it gives you information about what would have happened 10 billion years ago."

The findings also align with predictions from supercomputer simulations regarding galaxy evolution. These simulations suggest that typical disk-like galaxies contain fewer clumps, with most star formation occurring in smaller regions, as seen in the Milky Way today. Mergers create larger clumps, leading to an increase in star formation rates.

While star-forming clumps have been observed with the Hubble Space Telescope, it is the JWST's infrared capabilities that have allowed researchers to obtain unprecedented detail. The survey's results confirm the existence of massive clumps in the local universe, reinforcing the understanding of how these structures contribute to galaxy evolution.

As the universe has matured, galaxies have become more stable and settled, resulting in fewer examples of the violent mergers that characterized the early universe. However, the study of LIRGs and ULIRGs provides a window into this tumultuous past, revealing insights into how future galactic mergers, such as the anticipated collision between the Milky Way and Andromeda, may reignite massive star formation in our own galaxy.

In conclusion, the ongoing research into these ancient star factories not only enhances our understanding of galaxy formation and evolution but also helps astronomers anticipate the future dynamics of our own galaxy as it prepares for its eventual merger with Andromeda. The findings underscore the importance of continued exploration of the cosmic landscape, which remains rich with mysteries waiting to be uncovered.

The full results of this groundbreaking study are expected to be published in a forthcoming issue of The Astrophysical Journal, further contributing to the expanding knowledge of cosmic evolution and the nature of galaxies throughout the universe.