Five-galaxy merger soon after the Big Bang captured, James Webb Space Telescope discovers rare phenomena

Astronomers using the James Webb Space Telescope have identified a rare system of at least five galaxies merging in the early universe, approximately 800 million years after the Big Bang. The discovery combines data from both the James Webb Space Telescope and Hubble Space Telescope. The merger system, designated JWST's Quintet, represents an exceptionally uncommon phenomenon in cosmic observations and simulations.

JWST's Quintet contains five galaxies and 17 galaxy clumps

The newly discovered merger system includes at least five galaxies and 17 galaxy clumps embedded within a large gas halo. These emission-line galaxies display prominent hydrogen and oxygen signatures indicating active star formation.

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"Finding such a system with five physically linked galaxies is exceptionally rare, both in current simulations and in observations," said study lead author Weida Hu, a postdoctoral researcher at Texas A&M University.

"The probability of detecting even one [multiple-galaxy merger] is quite low, which raises the possibility that we may have been 'lucky' in identifying this system so early," Hu told Live Science in an email.

James Webb Space Telescope data reveals connected galaxy system

The James Webb Space Telescope's Near-Infrared Camera (NIRCam) detected a large gas halo surrounding the galaxy group, confirming the five galaxies are physically connected rather than independent systems.

While Hubble previously detected some galaxies in this region, "only JWST data tell us that the five galaxies have the same redshift and are interacting with each other," Hu added.

The research, published August 15 in Nature Astronomy, utilized combined observations from both space telescopes.

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Multiple galaxy mergers extremely rare in universe

Galaxy mergers involving more than two systems occur infrequently in cosmic observations. Christopher Conselice, a professor of extragalactic astronomy at the University of Manchester who was not involved in the study, provided context on merger frequency.

"If you look at all galaxies, then 20-30% of them will be in a merger. This will be just two galaxies. The fraction of these multiple merger systems will be much, much lower, and we don't have stats on it quite yet, but certainly lower than 1%," Conselice told Live Science.

The two main galaxies in JWST's Quintet are separated by 43,300 light-years, while the most distant pair spans 60,700 light-years.

JWST's Quintet compared to Stephan's Quintet system

The early universe merger system shares similarities with Stephan's Quintet, a local universe counterpart involving four merging galaxies plus one background galaxy.

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"A striking similarity is the presence of a bridge of material connecting two galaxies in JWST's Quintet, a feature also seen in Stephan's Quintet, indicative of tidal tails produced by the galaxy interaction," Hu said. "However, the star formation rate of JWST's Quintet is much higher."

The James Webb telescope observations show significantly more vigorous star formation in the early universe system compared to the older, less active galaxies in Stephan's Quintet.

Galaxy merger may form massive quiescent system

JWST's Quintet possesses a combined stellar mass equivalent to 10 billion suns. The high mass and star formation rate suggest the merging galaxies may evolve into a massive quiescent galaxy within 1 billion to 1.5 billion years after the Big Bang.

Quiescent galaxies cease forming new stars, and several have been detected in the early universe by previous James Webb Space Telescope studies.

The merger system could potentially explain how massive quiescent galaxies form rapidly through smaller galaxy combinations in the early universe.

Future James Webb Telescope surveys to study galaxy mergers

Additional James Webb telescope surveys may identify more systems similar to JWST's Quintet, enabling researchers to study the frequency and formation conditions of multiple galaxy mergers.

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"The fact that the galaxies are spatially close together is the indication that they probably will merge," Conselice said.

Future discoveries will help verify whether these systems represent rare phenomena predicted by current cosmological models or indicate previously unknown cosmic mechanisms.