JWST confirms a supermassive black hole is halting star formation in its host galaxy by ejecting vital star-forming gas.
James Webb Telescope Unveils Supermassive Black Hole Starving Its Host Galaxy
By Lydia Amazouz
Published on September 16, 2024 17:12
Astronomers using the James Webb Space Telescope (JWST) have confirmed that a supermassive black hole nearly 12 billion light-years away is actively starving its host galaxy, preventing it from forming new stars.
This discovery, published in Nature Astronomy on September 16, offers the first direct evidence that black holes can halt star formation by ejecting vital gas, leaving the galaxy dormant. The galaxy in question, GS-10578, also known as Pablo’s Galaxy, has stopped forming stars, a process known as "quenching," driven by the black hole at its core.
How a Supermassive Black Hole Starves Its Galaxy
At the heart of Pablo’s Galaxy, like many large galaxies, lies a supermassive black hole. These cosmic giants have long been known to influence their surroundings, but the exact relationship between black holes and star formation has remained elusive. In Pablo’s Galaxy, the black hole not only consumes nearby matter but also ejects vast streams of gas at incredible speeds—up to 1,000 kilometers per second. This outflow of gas, crucial for forming new stars, is being expelled from the galaxy so rapidly that it escapes the galaxy’s gravitational pull, leaving insufficient material behind to fuel star formation.
Dr. Francesco D’Eugenio, co-lead author of the study from the University of Cambridge, explained the significance of this finding: “The black hole is killing this galaxy and keeping it dormant by cutting off the source of ‘food’ the galaxy needs to form new stars.” The JWST’s ability to detect non-luminous gas—cold, dense gas that does not emit light—was key in observing these ejections. This gas, which previous telescopes could not detect, blocks light from a galaxy behind it, allowing scientists to determine its composition and mass. The mass of gas being expelled is greater than the amount needed to sustain star formation, confirming that the black hole is actively shutting down the galaxy's ability to create new stars.
The Implications for Understanding the Early Universe
Pablo’s Galaxy is located in the early universe, around 2 billion years after the Big Bang, a time when most galaxies were rapidly producing stars. Discovering a "dead" galaxy of this size at such an early period is particularly surprising to astronomers. Professor Roberto Maiolino, a co-author from the University of Cambridge, noted, “In the early universe, most galaxies are forming lots of stars, so it’s interesting to see such a massive dead galaxy at this period in time. If it had enough time to get to this massive size, whatever process that stopped star formation likely happened relatively quickly.”
The team’s findings challenge previous theories about how galaxies evolve. Until now, many models suggested that when star formation ceases in a galaxy, the process is violent and chaotic, often leaving the galaxy’s structure disrupted. However, Pablo’s Galaxy retains an orderly, disk-shaped structure, with its stars continuing to rotate smoothly, even though it is no longer forming new ones. This discovery suggests that the end of star formation might not always lead to galaxy-wide disruption.
Exploring the Mechanics of Black Hole-Driven Starvation
The study confirms long-standing theoretical models that suggested supermassive black holes can suppress star formation in their host galaxies, but until the JWST, direct observational evidence had been lacking. Using JWST’s advanced instruments, astronomers were able to observe that the galaxy’s black hole is expelling not only hot gas—typically seen in other galaxies with active black holes—but also colder, denser gas that is more crucial for star formation. This new wind component had previously gone undetected by earlier telescopes, further highlighting the JWST’s capabilities in exploring the early universe.
The ejected gas moves at such high speeds that it escapes the galaxy entirely, preventing the remaining material from cooling and condensing into new stars. This process effectively starves the galaxy of the resources it needs to form stars, leaving it in a "dead" state. The discovery of this mechanism, where a black hole can exert such a powerful influence over its galaxy, offers new insights into how galaxies evolve and how black holes shape their development.
As D’Eugenio emphasized, “We found the culprit. The black hole is killing this galaxy and keeping it dormant by cutting off the source of ‘food’ the galaxy needs to form new stars.” This finding helps solve a long-standing mystery in astronomy: how and why large galaxies like Pablo’s Galaxy stop forming stars while retaining their large sizes and overall structure.
Future Research on Black Hole and Galaxy Interactions
This discovery opens the door to more detailed studies of how black holes interact with their host galaxies, particularly in the early universe. While JWST has provided unprecedented detail about the quenching process in Pablo’s Galaxy, astronomers are eager to further investigate the surrounding region to determine if any star-forming gas remains or if other processes are at work. Future observations using the Atacama Large Millimeter/submillimeter Array (ALMA) will focus on detecting the coldest, darkest gas components that JWST may not have captured, providing a more comprehensive picture of the galaxy’s current state and the extent of the black hole’s influence.
In addition to studying Pablo’s Galaxy, astronomers hope to apply these findings to other galaxies with supermassive black holes. By understanding how black holes can quench star formation, researchers can better model the evolution of galaxies over time and assess the role black holes play in the growth and eventual "death" of galaxies.
As Professor Maiolino concluded, “We knew that black holes have a massive impact on galaxies, and perhaps it’s common that they stop star formation, but until Webb, we weren’t able to directly confirm this. It’s yet another way that Webb is such a giant leap forward in terms of our ability to study the early universe and how it evolved.”
This discovery is a major leap in our understanding of the cosmic life cycle of galaxies and the critical role that black holes play in shaping the universe. The JWST, with its unparalleled sensitivity and precision, continues to revolutionize our view of the cosmos, offering fresh insights into the early universe and how galaxies like our own Milky Way may have evolved billions of years ago.