Astronomers have observed a galaxy that suddenly stopped forming new stars more than 13 billion years ago. Using the James Webb Space Telescope, an international team of astronomers led by the University of Cambridge has detected a “dead” galaxy when the universe was only 700 million years old. It is the oldest such galaxy ever observed.

This galaxy appears to have lived fast and died young: Star formation occurred quickly and ended almost as quickly; This was unexpected for such an early stage in the evolution of the universe. However, it is not clear whether this galaxy’s “extinct” state is temporary or permanent and what caused the cessation of new star formation.

The results were published in the journal Nature may be important in helping astronomers understand how and why galaxies stop forming new stars and whether factors affecting star formation change over time. billions of years.

“The first few hundred million years of the universe were a very active phase in which many gas clouds collapsed to form new stars,” said Tobias Loeser of the Kavli Institute of Cosmology, the paper’s first author. “Galaxies need a large supply of gas to form new stars, and the early universe was like an all-you-can-eat buffet.”

Co-author Dr. from the Kavli Cosmology Institute. “Only later in the universe, through a black hole or something, do we start to see galaxies stop forming stars,” Francesco D’Eugenio said.

Astronomers believe that star formation can be slowed or stopped by a variety of factors; All of this will cause the galaxy to lack the gas needed to form new stars. Internal factors such as a supermassive black hole or star formation feedback can push gas out of the galaxy, causing star formation to quickly stop. On the other hand, during star formation, gas can be depleted very quickly without being quickly replenished with fresh gas from the galaxy’s surroundings, leading to starvation of the galaxy.

“We are not sure that any of these scenarios could explain what we are currently seeing in Webb,” said co-author Professor Roberto Maiolino.

“Until now, we have been using models based on the modern universe to understand the early universe. But now that we can see much further back in time and see that star formation stopped so rapidly in this galaxy, models based on the modern universe may need to be revised.”

Using JADES (JWST Advanced Deep Extragalactic Survey) data, astronomers determined that this galaxy experienced a brief, intense period of star formation between 30 and 90 million years ago. But between 10 and 20 million years before Webb observed it, star formation suddenly stopped.

“Events appear to occur faster and more dramatically in the early universe, and this may include galaxies transitioning from the star formation phase to the dormant or extinction phase,” Loeser said.

Astronomers have previously observed dead galaxies in the early universe; however, this galaxy is the oldest known to date; Just 700 million years after the Big Bang, more than 13 billion years ago. This observation is one of Webb’s most profound.

Besides being the oldest galaxy, this galaxy is also relatively low in mass; It is almost identical to the Small Magellanic Cloud (SMC), a dwarf galaxy near the Milky Way, but the SMC is still forming new stars. Other extinct galaxies in the early universe had much greater mass, but Webb’s improved sensitivity allows smaller, fainter galaxies to be observed and analyzed.

Although it appeared dead at the time of observation, astronomers say that after about 13 billion years, this galaxy may have come back to life and started forming new stars again.

“We’re looking for other galaxies like this in the early universe, which will help us put some constraints on how and why galaxies stop forming new stars,” D’Eugenio said. “Galaxies in the early universe may ‘die’ and then come back to life; we will need more observations to help us understand this.”