For a long time, astronomers believed that galaxies go out with something close to a cosmic bang, but a recent discovery hints that, in some cases, all you get is a whimper.
Using the James Webb Space Telescope, a group of scientists discovered a black hole that’s starving its host galaxy of the materials needed for star creation. While black holes have been known to kill individual stars, destruction on this scale is unprecedented. The discovery could have huge implications for our understanding of what happens to galaxies as they age.
The astronomers reached this stark conclusion after observing a galaxy called GS-10578, nicknamed Pablo’s Galaxy. They looked at Pablo’s Galaxy through the James Webb Space Telescope’s Near Infrared Spectrograph, which, as its name implies, observes light in the near-infrared range.
The JWST instrument allowed the astronomers to measure the speed of gas being expelled from Pablo’s Galaxy at around 621 miles (1,000 kilometers) per second. The massive clouds of gas are being expelled thanks to the force of a supermassive black hole.
This measurement alone wasn’t groundbreaking. The force of black holes often leads to galaxies expelling hot gas. But the JWST detected a second type of gas, which was colder and denser. Because the gas also didn’t emit light, the team was able to measure it by observing how much light from other galaxies it was blocking out.
Using those measurements, they deduced that these winds contained the materials necessary to feed star formation. When they compared the outflow of matter to the star formation rate, they found the outflow was larger. That led them to believe the supermassive black hole at the galaxy’s center was essentially starving the galaxy to death.
“Based on earlier observations, we knew this galaxy was in a quenched state: It’s not forming many stars given its size, and we expect there is a link between the black hole and the end of star formation,” said Francesco D’Eugenio, a postdoctoral researcher at Cambridge’s Kavli Institute for Cosmology, who led the study, in a statement. “However, until Webb, we haven’t been able to study this galaxy in enough detail to confirm that link, and we haven’t known whether this quenched state is temporary or permanent.”
Pablo’s Galaxy is named after astrophysicist and Center for Astrobiology researcher Pablo G. Pérez-González, who was one the scientists, including D’Eugenio, who described the discovery in a new paper, published in Nature Astronomy.
Previous models of the lifespan of galaxies predicted that, as they ran out of material to form stars, there would be a violent effect, which would distort their shape. But Pablo’s Galaxy shows no signs of that kind of turbulence. The existing stars are still going about their orbits as usual.
“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,” said Roberto Maiolino, D’Eugenio’s colleague at the Kavli Institute. “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.”
There are still big questions left to answer as to why Pablo’s Galaxy has defied expectations. It’s possible there is another source of star-making fuel that remains undetected, which could explain the lack of chaos, despite the galaxy seemingly being in the process of starving to death. Finding the answers could lead to new understanding about how galaxies form, and what awaits our own Milky Way when it, too, enters the galactic form of hospice.
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