James Webb telescope detects 'galaxy-killing wind' near the dawn of time — and it could preview the death of the Milky Way

When galaxies collide, it's less like a train wreck and more like a marriage: Two separate entities merge into a single massive celestial structure. But relationships are hard, whether you're a human or a galaxy — and ,this process may also "kill" the merging galaxies by unleashing star-quenching winds.

This mechanism may help to explain an enigma in the early universe. A glut of James Webb Space Telescope (JWST) observations have shown that galaxies grew surprisingly massive within 1 billion years of the Big Bang. Just as unexpectedly, many of these galaxies appear to have already stopped producing stars and grown quiescent (or dead) only about a billion years later.

Galactic winds have previously been considered as galaxy-killing culprits, but astronomers lacked the direct evidence to confirm that this process can meaningfully suppress star formation at such an early stage of cosmic history. Now, in a paper published June 10 in the journal Monthly Notices of the Royal Astronomical Society, an international team of astronomers has described how star-driven winds can quench galaxies, creating the kaleidoscope of quiescent structures observed by JWST.

Gas leak near the dawn of time

The researchers used JWST and the Atacama Large Millimeter/submillimeter Array radio telescope in Chile's Atacama Desert to observe a system of galaxies called CRISTAL-02 as it appeared only 1 billion years after the Big Bang.

With a stellar mass around 10 billion times greater than the sun's, CRISTAL-02 is a galactic merger that represents the latter stages of a multigalaxy collision. It also exhibits an immense plume of gas, almost as long as the galaxy system itself, that is escaping into space at hundreds of miles per second.

This immense outflow, comprising 1.5 billion solar masses, appears to be driven by the intense winds generated through a rapid burst of star formation, as well as star death, the study authors said. Both processes occur as galaxies collide, shocking large gas clouds into birthing new stars, including extremely massive ones that die within a few million years in violent supernova explosions.

The intense radioactive winds released from these young stars and their dying elder siblings can then suppress stellar formation, by energizing and dispersing pockets of cool molecular gas before it can gravitationally collapse to birth baby stars.

"The galaxy has a powerful wind that is ejecting material twice as fast as the galaxy forms stars," first author Rebecca Davies, an astrophysicist at the Swinburne University of Technology in Australia, said in a statement.

The CRISTAL-02 galaxy system may be forming around 260 new solar-mass stars per year — a rate three times higher than galaxies with similar masses and ages. Yet it's also losing more than 500 solar masses per year, — 20 times faster than typical massive galaxies, the researchers found.

"We don’t know much about how the first galaxies stopped forming stars. This work directly shows that process in action," co-author Andreas Faisst, an observational astronomer at Caltech, told Live Science via email.

"If the outflow keeps going, the galaxy will run out of gas to form stars in less than 100 million years from now — a blink of an eye in astrophysical terms."

A widespread cosmic phenomenon

This research offers a blueprint for galactic senescence, or gradual deterioration. "Almost half of early massive galaxies are interacting with other nearby galaxies, suggesting this isn't a quirk but a widespread cosmic phenomenon," Davies added.

But previous simulations have suggested that outflows from active black holes, rather than stars, may be primarily responsible for creating quiescent galaxies. Star-burst-driven outflows cease once star formation stops, whereas black-hole-driven outflows can persist for hundreds of millions of years afterward.

Therefore, the researchers cannot rule out that the CRISTAL-02 outflow was generated by a powerful black hole that was inactive at the time of the observation.

Additionally, the researchers compared the outflow from CRISTAL-02 with a sample of 99 other similar outflows spanning 12 billion years to determine whether this feedback process evolves over time.

They discovered that outflow efficiency has remained roughly constant across cosmic history, even as the internal properties of galaxies have changed while the universe has aged and expanded. Additionally, constraining the early-universe feedback mechanisms that dictate galactic evolution can help astronomers improve cosmological simulations that aim to explain why the cosmos looks and behaves the way it does today.

"If many early galaxies collide and experience rapid growth, then it may not be surprising that we see so many dead galaxies in the early universe," Davies explained. "CRISTAL-02 offers a natural solution to the mystery of why these massive galaxies live fast and die young."

These processes are still at work today, governing local star-dense sectors in our galaxy. They may also dictate its far off future, as the Milky Way could collide with our biggest neighbor, Andromeda, in around 4.5 billion years. When this merger occurs, it "will likely trigger a starburst associated with strong stellar winds — maybe similar to what we see in CRISTAL-02," Faisst said via email.

"The Milky Way and Andromeda system will subsequently likely become a large quiescent elliptical galaxy."