Astronomers have discovered one of the oldest “dead” galaxies ever seen—and its story is not one of sudden destruction, but of slow starvation.
Using the James Webb Space Telescope (JWST) and the Atacama Large Millimeter Array (ALMA), researchers found that a growing supermassive black hole can quietly cut off a galaxy’s fuel supply, stopping star formation over time rather than blowing the galaxy apart.
The galaxy, officially known as GS-10578 and nicknamed “Pablo’s galaxy,” existed about three billion years after the Big Bang.
Despite forming so early in the universe’s history, it is already massive, containing roughly 200 billion times the mass of the Sun.
Most of its stars were born quickly, between about 12.5 and 11.5 billion years ago, after which the galaxy mysteriously shut down.
Galaxies form new stars using cold gas, mainly hydrogen. But Pablo’s galaxy appears to have almost none left.
When the research team spent nearly seven hours observing it with ALMA, they expected to detect carbon monoxide, a key sign of cold gas.
Instead, they found nothing at all. This absence was striking and revealed that the galaxy had already run out of the raw material needed to make stars.
The likely cause is the supermassive black hole at the galaxy’s center. However, rather than destroying the galaxy in a single violent outburst, the black hole seems to have acted slowly and repeatedly.
Over time, it heated the gas around the galaxy or pushed it away, stopping fresh gas from flowing back in. The researchers describe this process as “death by a thousand cuts.”
JWST data provided another crucial clue. Spectroscopy showed strong winds of gas flowing outward from the black hole at speeds of about 400 kilometers per second.
These winds are carrying away roughly 60 times the mass of the Sun in gas every year. At that rate, the galaxy’s remaining fuel could be exhausted in as little as tens of millions of years—a blink of an eye in cosmic terms.
What makes this discovery even more surprising is the galaxy’s appearance. It looks calm and orderly, rotating like a disk, with no signs of a recent major collision with another galaxy.
This suggests that a dramatic merger did not shut down star formation. Instead, repeated periods of black hole activity likely kept reheating or expelling incoming gas, preventing the galaxy from refueling itself.
By reconstructing the galaxy’s history, the researchers found that fresh gas never truly returned once star formation slowed. The black hole didn’t need to remove all the gas at once—it only needed to block the supply.
This discovery helps explain why astronomers are now finding many massive, old-looking galaxies in the early universe, something that was unexpected before JWST began operations. The findings suggest that slow starvation by black holes may be a common way galaxies “live fast and die young.”
Future observations will study more galaxies like Pablo’s to see how widespread this process is and to better understand how black holes shape the life cycles of galaxies across cosmic time.
Source: University of Cambridge.
