A remarkable discovery is forcing astronomers to rethink fundamental theories about how quickly galaxies evolved in the early universe. Scientists have spotted what appears to be a fully-formed spiral galaxy, similar to our Milky Way, from just 1 billion years after the Big Bang.
Named Zhúlóng (meaning “Torch Dragon” in Chinese mythology), this ancient galactic structure bears an uncanny resemblance to the Milky Way, complete with spiral arms spanning about 62,000 light-years across. According to conventional wisdom, it shouldn’t exist this early in cosmic history.
But Zhúlóng shows that mature galaxies emerged much earlier than previously believed, in the first billion years after the Big Bang. The study, published in Astronomy & Astrophysics, was led by Dr. Mengyuan Xiao, a postdoctoral researcher at the University of Geneva (UNIGE).
“In the myth, Zhúlóng is a powerful red solar dragon that creates day and night by opening and closing its eyes, symbolizing light and cosmic time,’’ Xiao explains.
A Galaxy Before Its Time
Before the James Webb Space Telescope (JWST) began observing the distant cosmos, astronomers generally believed that galaxies in the early universe would be chaotic, asymmetrical collections of stars and gas. The orderly spiral patterns familiar to us were thought to take many billions of years to develop.
Yet there sits Zhúlóng, sporting a central bulge where star formation has already stopped, surrounded by an actively star-forming disk with distinct spiral arms — all existing when the universe was less than 8% of its current age.
The research team spotted Zhúlóng during observations with JWST’s Near Infrared Camera as part of the PANORAMIC survey. Using advanced imaging techniques, they confirmed the galaxy’s spiral structure and measured its properties.
“This discovery shows how JWST is fundamentally changing our view of the early Universe,” says Prof. Pascal Oesch, associate professor in the Department of Astronomy at the Faculty of Science of UNIGE and co-principal investigator of the PANORAMIC program.
Breaking All the Rules
Zhúlóng isn’t just remarkable for its shape, it’s also surprisingly massive. The researchers estimate it contains roughly 11 billion solar masses worth of stars, comparable to our Milky Way today.
“What makes Zhúlóng stand out is just how much it resembles the Milky Way – both in shape, size, and stellar mass,” says Xiao.
Reaching this size so quickly after the Big Bang requires extraordinary efficiency in converting gas into stars. The research team calculated that about 30% of all available ordinary matter in the galaxy’s dark matter halo had already turned into stars — roughly 1.5 times more efficient than even the most productive galaxies observed in later cosmic periods.
Another aspect that puzzles scientists is Zhúlóng’s unusual maturity. While most extremely massive galaxies from this early cosmic era are either compact with minimal star formation or wildly irregular with explosive star formation, Zhúlóng shows signs of settling down. Its central region appears reddish and no longer forming stars, while its spiral disk continues forming stars at a modest rate of about 66 solar masses per year, relatively calm for a galaxy of this epoch.
Rewriting Cosmic History
The existence of a galaxy with these characteristics so early in cosmic history raises profound questions about our models of galaxy formation. The universe at this time was much denser than today, with frequent galaxy collisions that typically disrupt orderly structures.
The discovery of Zhúlóng adds to mounting evidence from JWST observations that galaxy formation and evolution occurred much faster than previously theorized. Throughout its operation, JWST has repeatedly revealed galaxies that are bigger, more structured, and more mature than expected at various cosmic distances.
This remarkable galaxy demonstrates that the universe could produce structures resembling modern spiral galaxies like our Milky Way in just a fraction of the time we thought necessary, suggesting we need to revise our understanding of cosmic evolution.
“How a morphologically mature galaxy that resembles nearby massive spirals can form in this environment remains an open question,” the authors write, “but the discovery of this source is a first step and provides an important constraint on galaxy formation models.”
Source : https://studyfinds.org/milky-way-twin-discovered-infant-universe/
