An international team led by the University of Geneva (Uniguet) has discovered the most remote Spiral Galaxy candidate known to date.
Formation just a billion years after the Big Bang, the Milky Way-like spiral galaxy exhibits a very mature structure with old bulging in the middle, a large star-forming disc and a well-defined spiral arm.
This discovery is made using data from James Webb Space Telescope (JWST) and provides important insights into how galaxies quickly form and evolve in the early universe.
The history of the spiral galaxy
Large spiral galaxies like the Milky Way are expected to take billions of years to form.
For the first billion years of universe history, galaxies were considered small, chaotic and irregular.
However, JWST is beginning to reveal very different drawings. Its deep infrared imaging reveals surprisingly large and well-structured galaxies much earlier than previously expected, prompting astronomers to reevaluate how and how galaxies shaped in early universes.
Milky Way twins?
Among these new findings is Zhúlóng, the most distant spiral galaxy candidate ever identified, at a redshift of 5.2, just a billion years after the Big Bang.
Despite this early period, distant galaxies exhibit surprisingly mature structures. Old bulge in the middle, large star-forming discs, spiral arms – features that are usually found in nearby galaxies.
Dr. Mengyuan Xiao, a postdoctoral researcher in the Department of Astronomy at Unige’s Faculty of Science, and the lead author of the study explained:
“The disc spans over 60,000 light years, comparable to our own galaxy, and the star contains over 100 billion solar masses.”
These features make it one of the most compelling Milky Way analogs discovered at such an early age, raising new questions about how a large, ordered spiral galaxy forms just after the Big Bang.
The importance of JWST’s unique “pure parallel” mode
Zhúlóng was discovered during deep imaging of the Panoramic Survey (GO-2514) at JWST. This is a wide, regional, non-regional galaxy program led by Christina Williams (Neal Love) and Pascal Osh (Unige).
Unique “Pure Parallel” Mode of Panoramic Exploite JWST – Efficient Strategies to Collect High Quality Images The main equipment of JWST acquires data about different targets.
“This allows JWST to map large areas of the sky, which is extremely rare and is essential for discovering large galaxies,” explained Christina Williams.
“This finding highlights the possibility of pure parallel programs to reveal rare and distant objects that stress-test galaxy formation models.”
Rewrite the history of the spiral galaxy
Spiral galaxies were previously thought to take billions of years to develop. Furthermore, large galaxies were not expected to exist much later in the universe. This is because they usually form after small galaxies fuse over time.
“This discovery shows that JWST is fundamentally changing the way we view the universe in its early days,” Professor Pascal Osch said.
Future JWST and Atacama large-scale millimeter array (ALMA) observations will help to confirm their properties and further clarify their formation history. As JWST investigations of new and wide regions continue, astronomers hope to find more such galaxies, providing fresh insights into the complex processes that form early cosmic galaxies.
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