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Discovery of mature galaxy rewrites cosmic history
Astronomers in India have identified a fully formed spiral galaxy dating back to when the Universe was just 1.5 billion years old, defying long-held assumptions about early cosmic evolution. The finding, made using the James Webb Space Telescope (JWST), suggests galaxies developed complex structures far earlier than previously thought.
The unexpected find
Researchers Rashi Jain and Yogesh Wadadekar spotted the galaxy while analyzing JWST data. Named Alaknanda after a Himalayan river, it resembles the Milky Way in structure despite existing when the Universe was only 10% of its current age. The discovery was published in Astronomy and Astrophysics in November.
"The galaxy looks remarkably similar to our own Milky Way, despite its extreme youth by cosmic standards," said Professor Wadadekar, co-author of the study.
Yogesh Wadadekar, Tata Institute of Fundamental Research
Cosmic implications
Alaknanda spans approximately 30,000 light-years, about one-third the size of the Milky Way, and contains roughly 10 billion stars. Its symmetrical spiral arms and central bulge mirror modern galaxies, contradicting theories that early galaxies were predominantly irregular and chaotic.
"This galaxy assembled 10 billion solar masses of stars and formed a large disc with spiral arms in just a few hundred million years-an astonishingly rapid process," Wadadekar told the BBC. Current star formation rates in Alaknanda are 20-30 times higher than those in the Milky Way today.
Revising early Universe models
The discovery adds to growing evidence that the early Universe was more structured than once believed. JWST, launched in 2021, has revealed increasingly sophisticated galaxies, including spirals, challenging traditional timelines of cosmic evolution.
"Finding such a well-formed spiral galaxy so early in the Universe is a rare exception, but these exceptions force us to rethink how galaxies formed and evolved," said Jain, a PhD researcher at the National Centre for Radio Astrophysics (NCRA-TIFR) in Pune.
Rashi Jain, NCRA-TIFR
Jain identified Alaknanda while examining data from 70,000 celestial objects, noting its distinctive "beads-on-a-string" pattern of star clusters along its arms.
Unanswered questions
The galaxy's light has traveled 12 billion years to reach Earth, offering a glimpse into the past but leaving its current state unknown. Researchers plan follow-up observations using JWST or the ALMA observatory in Chile to study how Alaknanda developed its spiral structure.
"The keys to our present and future lie in the past," Wadadekar said. "Understanding this galaxy could reshape our models of cosmic history."
