Astronomers Observe the Gradual Decline of Massive Galaxy GS-10578 in the Early Universe

Astronomers have documented a rare phenomenon in the early cosmos: the massive galaxy GS-10578, nicknamed "Pablo’s Galaxy," which has begun a slow transition toward dormancy. This cessation of star formation is attributed to the depletion of cold gas reserves approximately three billion years after the Big Bang. A 2026 study, utilizing data from the James Webb Space Telescope (JWST) and the Atacama Large Millimeter/submillimeter Array (ALMA), revealed that a central supermassive black hole is actively blocking the influx of gas required to birth new stars.

Despite its ancient origins, GS-10578 is remarkably massive, possessing a stellar mass equivalent to roughly 200 billion Suns. Its primary era of star formation occurred between 12.5 and 11.5 billion years ago, indicating an incredibly intense initial growth phase. Rather than a sudden collapse, the galaxy is undergoing a process described by researchers as "death by a thousand cuts." This gradual suppression of star-making activity provides a vital explanation for the increasing number of mature, massive galaxies being discovered by JWST in the early universe.

A research team led by scientists from the University of Cambridge determined that the central black hole repeatedly heated and expelled surrounding gas. This created a "zero-fluid flow" scenario where no new stellar material could accumulate. Spectroscopic data from JWST identified powerful winds of neutral gas surging at speeds of 400 kilometers per second, resulting in the loss of approximately 60 solar masses of gas every year. At this rate, the galaxy's remaining fuel could be entirely exhausted within a window of 16 to 220 million years—a mere blink of an eye in cosmological terms.

Complementary observations from ALMA, which targeted carbon monoxide as a proxy for cold hydrogen, confirmed a severe shortage of star-forming fuel. Dr. Jan Scholz from the Cavendish Laboratory, a co-author of the study, emphasized that the absence of cold gas serves as definitive proof of "slow strangulation" rather than a catastrophic event. Interestingly, Pablo’s Galaxy maintains a highly organized stellar disk, suggesting that the suppression mechanism did not destroy the galaxy's physical structure. This finding highlights how supermassive black holes can shape the early universe through subtle, long-term processes.

The collaboration between JWST and ALMA, as detailed in Nature Astronomy, underscores the effectiveness of these instruments in mapping the evolutionary paths of ancient galaxies. While feedback from active galactic nuclei (AGN) is a known factor in the local universe, this evidence suggests such internal mechanisms were dominant even in the universe's infancy. Future JWST investigations focusing on hot hydrogen will be essential to further clarify the intricate details of how star formation is suppressed in these massive cosmic structures.