Oldest ‘Dead’ Galaxy in Universe Discovered

Astronomers have found a galaxy that stopped producing stars over 13 billion years ago, making it the earliest ‘dead’ galaxy ever detected. The discovery was made using the James Webb Space Telescope by a global team led by the University of Cambridge.

The galaxy, named JADES-GS-z7-01-QU and described in a paper published in the journal Nature, provides astronomers with a peek into the elusive underpinnings of galaxy evolution in a primordial universe, including why galaxies stop forming new stars and whether forces driving their starbursts alter across epochs.

A cosmic relic

The galaxy appears to have lived fast and died young: star formation happened quickly and stopped almost as quickly, which is unexpected for so early in the universe’s evolution. However, it is unclear whether this galaxy’s ‘quenched’ state is temporary or permanent, and what caused it to stop forming new stars.

“This galaxy challenges our understanding of how galaxies form and evolve in the early universe,” said Tobias Looser from the Kavli Institute for Cosmology, Cambridge (KICC), the paper’s first author. “It’s only later in the universe that we usually start to see galaxies stop forming stars, whether that’s due to a black hole or something else.”

Astronomers believe that star formation can be slowed or stopped by different factors, all of which will starve a galaxy of the gas it needs to form new stars. Internal factors, such as a supermassive black hole or feedback from star formation, can push gas out of the galaxy, causing star formation to stop rapidly. Alternatively, gas can be consumed very quickly by star formation, without being promptly replenished by fresh gas from the surroundings of the galaxy, resulting in galaxy starvation.

“We’re not sure if any of those scenarios can explain what we’ve now seen with Webb,” said co-author Professor Roberto Maiolino. “Until now, to understand the early universe, we’ve used models based on the modern universe. But now that we can see so much further back in time, and observe that the star formation was quenched so rapidly in this galaxy, models based on the modern universe may need to be revisited.”

A powerful vision

The discovery of this ancient galaxy was made possible by the Webb Telescope’s powerful infrared vision. The telescope launched in December 2021 from French Guiana and is currently orbiting about 1.5 million kilometres from Earth.

The telescope can peer through the thick veil of dust obscuring the earliest objects in the universe. In addition to being the oldest ‘dead’ or ‘quenched’ galaxy spotted so far, the newfound galaxy is also many times lighter than other similarly quiescent galaxies previously found in the early universe.

“Webb has opened a new window into the early universe,” said co-author Dr Francesco D’Eugenio, also from KICC. “It allows us to see galaxies that were previously invisible or too faint to detect with other telescopes.”

The researchers used data from JADES (JWST Advanced Deep Extragalactic Survey), one of the largest surveys conducted by Webb. JADES aims to observe thousands of galaxies across cosmic time, from just 200 million years after the Big Bang to today.

The researchers plan to use Webb to further study JADES-GS-z7-01-QU and other similar galaxies to understand their origin and fate. They also hope to find more examples of such early ‘dead’ galaxies and determine how common they are in the early universe.

“Finding this galaxy is like finding a needle in a haystack,” said Looser. “But it shows that there are still surprises waiting for us in the distant cosmos.”

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