Extremely rare 5-way galaxy merger spotted by JWST

 Astronomers surprised by an extremely rare 5-way galaxy merger in the early universe spotted by JWST    

Galaxy merger is a crucial process in galactic evolution which has happened since the first galaxies came into being. Now JWST has spotted a truly incredible group of five galaxies merging in the early universe. These merging weirdos are star-forming powerhouses. A rare five-galaxy merger spotted by the James Webb Space Telescope is reshaping how astronomers understand the universe’s earliest years. The JWST has identified an extraordinary system of five galaxies merging when the universe was only about 800 million years old, according to a new study. The discovery reveals a level of cosmic complexity which challenges long-standing models of early galaxy formation and suggests that large, dynamic structures emerged far earlier than expected. This level of crowding was assumed to be rare in the universe’s infancy, a time when galaxies were thought to be smaller, simpler, and more isolated. As lead author Dr. Weida Hu of Texas A&M University explained, “What makes this remarkable is that a merger involving such a large number of galaxies was not expected so early in the universe’s history, when galaxy mergers were thought to [be] simpler and usually involve only two to three galaxies.” The finding points to a far more dynamic early universe than theoretical models had predicted.

Because it takes time for light to travel large distances, the quintet's collision in the far-off reaches of space happened when the universe was just 800 million years old. Such a five-way merger would be rare anywhere in the universe, but even moreso during its youth, making this a surprise for astronomers. “What makes this remarkable is that a merger involving such a large number of galaxies was not expected so early in the universe’s history, when galaxy mergers were thought to [be] simpler and usually involve only two to three galaxies,” lead author Dr. Weida Hu, from Texas A&M University, said. The newly observed system consists of five compact, actively star-forming galaxies packed into a remarkably small region of space. Their proximity indicates that they are gravitationally bound and in the process of merging, forming what astronomers describe as an extreme and unexpected configuration for such an early epoch. Observations from JWST show that the galaxies are separated by only tens of thousands of light-years, a distance that places them far closer together than most neighboring galaxies in the modern universe.

When a big galaxy snatches a smaller one, it can rejuvenate the larger object. The collision between two galaxies of similar sizes creates new geometry, often turning spirals into elliptical galaxies. If the number wasn't enough of a surprise, the astronomers report that the system is enriched with heavier elements, such as oxygen, at a level not expected until 1 billion years after the Big Bang. These elements are formed by nuclear fusion inside stars, and their abundance appears to be a result of these galaxies producing stars at a rate of 250 solar masses/year, far higher than the average at the time. Beyond the sheer number of galaxies involved, the system stands out for its physical and chemical properties. The galaxies are producing stars and far exceeds typical star formation rates at that time. This rapid stellar production has enriched the system with heavier elements such as oxygen, materials forged in stellar interiors and dispersed through galactic interactions. The presence of these elements indicates that multiple generations of stars had already lived and died, enriching both the galaxies and their surrounding environment. Data analyzed from Nature Astronomy show that gas containing oxygen and hydrogen extends beyond the galaxies themselves, suggesting that gravitational interactions are pushing enriched material into intergalactic space. This process highlights how early mergers may have shaped not only galaxies, but also the larger cosmic environment they inhabit.

The galaxies are separated by just tens of thousands of light-years, which means the whole group occupies a relatively small volume of space. By comparison, the closest galaxies to the Milky Way, the dwarf galaxies known as the Large and Small Magellanic Clouds, are over 160,000 light-years away. Andromeda, which may be doomed to merge with our galaxy in the distant future, is over 2.5 million light-years away. Standard models of galaxy assembly propose a gradual buildup, where small galaxies merge over long periods of time to form larger systems. The five-way merger disrupts this picture by demonstrating that complex, multi-galaxy interactions were already underway. The discovery implies that matter in the early universe clustered more rapidly and efficiently than simulations have suggested. Coauthor Professor Casey Papovich emphasized the broader implications of the finding, stating, "By showing that a complex, merger-driven system exists so early, it tells us our theories of how galaxies assemble, and how quickly they do so, need to be updated to match reality.” The result strengthens growing evidence from JWST that the early universe was capable of producing massive, mature-looking galaxies at astonishing speed.

The team was also able to show the presence of oxygen and hydrogen around the galaxies. Oxygen can only have formed within the galaxies, where stars are enriching the interstellar medium. The interactions between the members of the quintet might have thrown the elements into intergalactic space, showing that even back then, mergers played a major role in shaping both galaxies and their environments. JWST has previously identified massive galaxies in the early universe that look surprisingly mature. If merging events similar to this were common, they could have driven the formation of those other unexpected objects. Clearly, the early universe remains a mystery, and further observations from JWST are needed.

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Results of melting Antarctic ice

West Antarctic ice-shelf melting did the opposite of what was expected 

As West Antarctica lost ice during past warm periods, icebergs dumped large amounts of iron into the Southern Ocean, but algae growth didn’t surge as expected. Scientists studying ancient ocean sediments discovered a surprising link between the shrinking of West Antarctica’s ice and the Southern Ocean’s ability to absorb CO2. Ocean-driven melting of floating ice-shelves in the Amundsen Sea is currently the main process controlling Antarctica’s contribution to sea-level rise. Using a regional ocean model, a comprehensive suite of future projections of ice-shelf melting in the Amundsen Sea is presented. It was found that rapid ocean warming, at approximately triple the historical rate, is likely committed over the twenty-first century, with widespread increases in ice-shelf melting, including in regions crucial for ice-sheet stability. When internal climate variability is considered, there is no significant difference between mid-range emissions scenarios and the most ambitious targets of the Paris Agreement. These results suggest that mitigation of greenhouse gases now has limited power to prevent ocean warming which could lead to the collapse of the West Antarctic Ice Sheet.

A new study finds that shifts in the West Antarctic Ice Sheet (WAIS) closely followed changes in marine algae growth in the Southern Ocean during past ice ages. However, the relationship did not work in the way scientists long assumed. The link centers on iron-rich sediment carried into the ocean by icebergs breaking away from West Antarctica. Iron typically acts as a nutrient which supports algae growth. But when researchers examined a sediment core collected in 2001 from the Pacific sector of the Southern Ocean, taken from more than three miles below the ocean surface, they found something surprising. Even when iron levels were high, algae growth did not increase. “Normally, an increased supply of iron in the Southern Ocean would stimulate algae growth, which increases the oceanic uptake of CO2,” says lead author Torben Struve of the University of Oldenburg. Struve worked as a visiting postdoctoral research scientist in 2020 at the Lamont-Doherty Earth Observatory, which is part of the Columbia Climate School.

In waters surrounding Antarctica, iron is often the nutrient which limits algae growth. Previous research has shown that during glacial periods, strong winds carried iron-rich dust from continental landmasses into the ocean. In areas north of the Antarctic Polar Front, a boundary where cold Antarctic waters meet warmer waters to the north, that dust helped fertilize algae. As algae growth increased, the ocean absorbed more CO2 from the atmosphere. This additional carbon uptake contributed to global cooling as ice ages began. The new study focuses instead on waters south of the Antarctic Polar Front. There, sediment evidence shows that iron delivery peaked during warmer periods rather than during glacial phases. The size and composition of particles in the core also revealed that the primary source of iron was not windblown dust, but icebergs calved from West Antarctica. “This reminds us that the ocean’s ability to absorb carbon isn’t fixed,” says co-author Gisela Winckler, a professor at the Columbia Climate School and a geochemist at the Lamont-Doherty Earth Observatory.

All scenarios exhibit significant and widespread future warming of the Amundsen Sea and increased melting of its ice shelves. The spatial distribution of trends for the Paris 2 °C scenario show mid-depth temperature (200–700 m mean), the water which directly affects the ice-shelf cavities. Indeed, trends in mid-depth temperature significantly correlate with trends in ice-shelf basal mass loss. In reality, basal mass loss will also depend on other factors we cannot account for in our simulations, such as changes in ice-shelf geometry. To explain the mismatch, the research team examined the chemical makeup of the sediment delivered by icebergs. Their analysis showed that much of the iron was highly “weathered,” meaning it had been chemically altered over long periods of time. During earlier warm phases, when more ice broke off from West Antarctica and drifted northward, much of the iron reaching the ocean was in this poorly soluble form. Because algae struggle to use this type of iron, the increased supply did not lead to higher biological productivity. Based on these findings, the researchers conclude that continued shrinking of the West Antarctic Ice Sheet could reduce the Southern Ocean’s ability to absorb CO2 in the future.

Future warming and melting are markedly stronger than historical trends, with ensemble mean future warming trends ranging from 0.8 to 1.4 °C per century compared with the historical mean of 0.25 °C per century. Even under the most ambitious mitigation scenario, Paris 1.5 °C, the Amundsen Sea warms three times faster than in the twentieth century. Comparison shows that local atmospheric changes are the main driver of Amundsen Sea warming, with remote ocean forcing playing a non-negligible secondary role. The findings also shed light on how sensitive the West Antarctic Ice Sheet is to rising temperatures. According to Struve, several recent studies suggest that this region experienced large-scale ice retreat during the last interglacial period about 130,000 years ago, when global temperatures were similar to today. “Our results also suggest that a lot of ice was lost in West Antarctica at that time,” says Struve. As the ice sheet, which reached several miles thick in some areas, broke apart, it produced large numbers of icebergs. These icebergs scraped sediment from the rock beneath the ice and released it into the ocean as they drifted north and melted. The sediment core indicates especially high iceberg activity at the end of glacial periods and during peak interglacial conditions.

“What matters here is not just how much iron enters the ocean, but the chemical form it takes,” says Winckler. “These results show that iron delivered by icebergs can be far less bioavailable than previously assumed, fundamentally altering how we think about carbon uptake in the Southern Ocean.” The researchers believe that beneath the West Antarctic Ice Sheet lies a layer of very old, heavily weathered rock. When the ice sheet retreated during earlier interglacial periods, icebergs carried large amounts of these weathered minerals into the nearby South Pacific. Despite the increased iron supply, algae growth remained low. “We were very surprised by this finding because in this area of the Southern Ocean, the total amount of iron input was not the controlling factor for algae growth,” Struve says. As global warming continues, further thinning of the West Antarctic Ice Sheet could recreate conditions similar to those of the last interglacial period. “Based on what we know so far, the ice sheet is not likely to collapse in the near future, but we can see that the ice there is already thinning,” says Struve. Continued retreat could speed up the erosion of weathered rock by glaciers and icebergs. This process could further reduce carbon uptake in the Pacific sector of the Southern Ocean compared with today, a feedback which could further amplify climate change in future ahead.

Muhammad (Peace be upon him) Name