Scientists said that the telescope observed a galaxy that had already stopped forming stars about 13.1 billion years ago. Many dead galaxies have been observed over the years, but these are the oldest, at about 500 million years.
“It appears that the galaxy lived a fast and violent life and then stopped forming stars very quickly,” said Tobias Loser, an astrophysicist from the Kavli Institute of Cosmology at the University of Cambridge and the lead author of the study published in the scientific journal Nature.
“For the first few hundred million years of its history, the universe was violent and active, and gas was abundant to power star formation in galaxies. That makes this discovery very puzzling and interesting,” he added.
After galaxies stop forming stars, they become a bit of a stellar graveyard.
“Once star formation ends, the existing stars die and are not replaced,” said Francesco Di Eugenio, an astrophysicist at the Kavli Institute. “This happens in a hierarchical manner, arranged by stellar weight, because the most massive stars are the hottest and brightest, and as a result they are the shortest-lived.”
Di Eugino added, “As the hottest stars disappear, the color of the galaxy changes from blue, which is the color of hot stars, to yellow and then red, which is the color of smaller stars.”
He continued, “Stars with the mass of the Sun live for about ten billion years. If this galaxy stopped forming stars at the time we observed it, there would be no Sun-like stars left in it at the present moment. But stars much smaller than the mass of the Sun can live for trillions of years, so, “They can continue to shine long after star formation has stopped.”
Sharp activity then sudden stop
The researchers determined that this galaxy went through a burst of star formation that lasted from 30 to 90 million years and then suddenly stopped. And they are trying to find out why.
Researchers say that this may be due to the impact of a supermassive black hole in the center of the galaxy or to a phenomenon called “feedback”, which is a burst of energy emanating from newly forming stars, which pushed the gas needed to form new stars out of the galaxy.
“Instead, the gas could be consumed very quickly by star formation, without the immediate supply of new gas from the surrounding galaxy, leading to the death of the galaxy,” Loser said.
In the new study, the researchers were able to observe the dead galaxy during a certain moment in time. They stated that it likely later resumed star formation.
“Some galaxies may undergo a renewal process if they can find new gas to turn into new stars,” Di Eugenio said. “We don't know the ultimate fate of this galaxy. This may depend on the mechanism that caused star formation to stop.”
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