In a stunning find, astronomers using the James Webb Space Telescope (JWST) have discovered a spiral galaxy so eerily similar to our own Milky Way that it’s been dubbed a “long-lost twin.” The galaxy, named Zhúlóng, dates back to just 1 billion years after the Big Bang, making it the most distant spiral galaxy ever observed. The discovery, detailed in the journal Astronomy & Astrophysics, is forcing scientists to rethink how quickly galaxies like ours could form in the early universe.
Zhúlóng shows all the structural hallmarks of a mature spiral galaxy—including a dense bulge of older stars and sweeping spiral arms—features that shouldn’t exist so early in cosmic history. This challenges the long-standing belief that large galaxies take billions of years to grow through slow mergers and star formation.
A Fully Formed Galaxy at the Dawn of Time
Zhúlóng stands out not just for its age but for its surprising maturity. At around 60,000 light-years wide, it’s only slightly smaller than the Milky Way’s 100,000 light-year diameter. Its stellar mass—100 billion solar masses—further solidifies its status as a full-fledged galactic sibling. Researchers were astonished to find such a structure so soon after the universe’s birth.
“This discovery shows how JWST is fundamentally changing our view of the early universe,” said Pascal Oesch, study co-author and associate professor at the University of Geneva. Zhúlóng appeared unexpectedly during JWST’s PANORAMIC survey, which uses the telescope’s “pure parallel” mode to simultaneously observe multiple patches of deep space.
Changing the Timeline of Cosmic Evolution
What’s baffling scientists most is how Zhúlóng could have formed so quickly and with such structural maturity. According to the Lambda-CDM model, the most widely accepted cosmological theory, galaxies of this size and complexity should take several billion years to develop through hierarchical merging—the gradual coalescence of smaller protogalaxies into larger systems. The Milky Way, for instance, is believed to have taken more than 8–10 billion years to form into its current spiral structure.
Yet Zhúlóng appears to have reached a similar configuration in less than a billion years, challenging assumptions about the speed and scale of galactic evolution in the early universe. It joins a growing list of early galaxies and supermassive black holes discovered by JWST that seem to have “grown up” too fast.
This raises fundamental questions: Are the models incomplete, or is something missing in our understanding of how dark matter, gas dynamics, and star formation operated in the early cosmos? These findings are driving theorists to revisit models of early-universe structure formation and consider more exotic possibilities, such as enhanced gas cooling or even modifications to gravity.
What Comes Next for Zhúlóng
Astronomers now plan a series of follow-up observations to investigate Zhúlóng in greater detail. One key objective is to measure the galaxy’s metallicity—the abundance of elements heavier than hydrogen and helium—which can reveal how many generations of stars have already lived and died there. If the galaxy is already metal-rich, it would indicate a surprisingly mature chemical history so early in cosmic time.
Future observations with JWST’s spectroscopic instruments and the Atacama Large Millimeter/submillimeter Array (ALMA) will also aim to examine the dynamics of gas within the galaxy’s disk, the rate of ongoing star formation, and the presence (or absence) of a central supermassive black hole.
These efforts could help determine whether Zhúlóng is a rare outlier—or a sign that our entire model of galaxy formation needs to be updated. For now, it stands as one of the clearest examples of how the James Webb Space Telescope is not just showing us the distant past—it’s reshaping how we understand the universe itself.
Source: The Daily Galaxy / Digpu NewsTex