A pair of researchers in Pune (India) has identified one of the most surprising galaxies yet uncovered by the James Webb Space Telescope: a fully formed spiral system that existed when the Universe was just 1.5 billion years old. The discovery, published in Astronomy & Astrophysics, challenges long-standing ideas about how quickly galaxies can assemble stable structures.
The galaxy, named Alaknanda, appears roughly 12 billion light-years away in images collected by JWST as part of the UNCOVER and MegaScience surveys. The researchers chose the name after the Alaknanda River, one of the Himalayan headstreams of the Ganga. Since the Milky Way is known as Mandakini in Hindi, they saw the distant spiral as a fitting “sister” to our own galaxy.
Alaknanda stands out because it displays a textbook “grand-design” spiral pattern, complete with two clean, symmetric arms winding around a compact central bulge—structures previously assumed to take several billion years to develop.
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Rashi Jain and Yogesh Wadadekar of the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research (NCRA-TIFR) led the analysis. By examining observations across 21 JWST filters, they could estimate Alaknanda’s distance, stellar mass, dust content, and star-formation history with unusual precision. Their calculations show that the galaxy spans about 30,000 light-years and contains around ten billion solar masses of stars, with star formation proceeding at a rate nearly 20 times faster than in today’s Milky Way. About half of its stars formed within only 200 million years — a snap in cosmic time.
Its appearance in such an early cosmic era is what makes Alaknanda so striking. Astronomers generally expect early galaxies to be irregular, clumpy, and turbulent as they assemble through rapid star formation and repeated collisions with other galaxies.
“Finding such a well-organised spiral disk at this epoch shows that the physical processes driving galaxy formation—gas accretion, disk settling, and possibly the development of spiral density waves—can operate far more efficiently than current models predict. It’s forcing us to rethink our theoretical framework,” said Rashi Jain, the study’s lead author.
A major factor aiding the discovery was gravitational lensing. The galaxy lies behind the massive cluster Abell 2744, also known as Pandora’s Cluster, whose enormous gravity bends and magnifies the light of background objects, making Alaknanda appear brighter and allowing JWST to resolve its structure in detail.
The finding adds to a growing body of evidence from JWST that the early Universe was more orderly and productive than earlier telescopes could reveal. The study’s co-author Yogesh Wadadekar said, “Alaknanda reveals that the early Universe was capable of far more rapid galaxy assembly than we anticipated.” Several disk-like galaxies have already been spotted at similar distances, but Alaknanda is among the clearest examples of a grand-design spiral at such a young epoch.
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The next phase will involve measuring the motion of gas and stars within the galaxy using JWST’s spectroscopic instruments or the ALMA observatory in Chile. These measurements could determine how fast Alaknanda is rotating and whether its disk rotates smoothly—indicating a dynamically “cold” system—or whether turbulence is still shaping it. “Understanding whether Alaknanda’s disk is cold or hot will tell us which formation mechanism created the spiral arms,” Wadadekar said.
For researchers, the galaxy is more than an anomaly. It is a signal that the Universe was capable of building stable, organised systems much earlier than expected. As JWST continues to probe deeper into cosmic history, discoveries like Alaknanda may force substantial revisions to models of galaxy formation and the timeline of early cosmic evolution.
The discovery was published in Astronomy & Astrophysics.