The galaxy was found in JWST images obtained as part of the UNCOVER and MegaScience surveys, which provided data in 21 different filters spanning a wide range of wavelengths. This multi band coverage enabled researchers Rashi Jain and Yogesh Wadadekar at the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research in Pune, India, to estimate Alaknandas distance, dust content, stellar mass, and star formation history with high precision.
Alaknanda displays the hallmark structure of a grand design spiral galaxy, with two symmetric spiral arms wrapped around a rounded central bulge. The system spans roughly 30,000 light years and contains about ten billion solar masses in stars, comparable to a substantial present day disk galaxy. Its spiral arms and bulge indicate that gas has already settled into an ordered rotating disk and that large scale patterns such as spiral density waves are shaping its structure.
The galaxy is also undergoing rapid star formation. Each year Alaknanda forms new stars with a combined mass of about 60 times the mass of the Sun, a rate around 20 times higher than in the Milky Way today. Roughly half of its stellar mass appears to have formed within a period of about 200 million years, indicating an intense build up phase over a brief interval in cosmic terms.
Jain, the lead author, noted that Alaknanda shows a level of structural maturity usually associated with galaxies that are billions of years older, implying that key processes in galaxy formation can proceed more efficiently than many current models allow. "Alaknanda has the structural maturity we associate with galaxies that are billions of years older," explains Rashi Jain, the study's lead author. "Finding such a well-organised spiral disk at this epoch tells us 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."
Alaknanda lies behind the massive galaxy cluster Abell 2744, also known as Pandoras Cluster, whose gravity acts as a natural gravitational lens. The clusters mass bends and magnifies light from distant cosmic objects in its background, making Alaknanda appear about twice as bright and allowing JWST to resolve its spiral pattern in detail. This gravitational lensing effect was essential to measuring the galaxys structure at such a large distance.
By combining the lensing amplification with JWSTs sensitivity and broad wavelength coverage, Jain and Wadadekar could reconstruct Alaknandas intrinsic properties and place it within the broader population of early galaxies. Their work shows that several disk like systems have already been found at similar epochs, but Alaknanda stands out as one of the clearest grand design spirals with two prominent, symmetric arms identified so far at this distance.
Co author Yogesh Wadadekar emphasized how quickly the galaxy assembled its mass and ordered structure. "Alaknanda reveals that the early Universe was capable of far more rapid galaxy assembly than we anticipated," says Yogesh Wadadekar, the study's co-author. "Somehow, this galaxy managed to pull together ten billion solar masses of stars and organise them into a beautiful spiral disk in just a few hundred million years. That's extraordinarily fast by cosmic standards, and it compels astronomers to rethink how galaxies form."
Researchers are now considering how Alaknandas spiral arms formed so early. One scenario involves steady infall of cold gas that fuels star formation and allows spiral density waves to develop naturally in a dynamically cold disk. Another possibility is a gravitational interaction with a smaller companion that triggered the spiral pattern, although such tidally induced spirals often fade relatively quickly.
Future observations will test these ideas by probing the galaxys internal motions. Spectroscopic measurements with JWST instruments or the Atacama Large Millimeter Array in Chile could determine how fast Alaknanda rotates, how its gas and stars move within the disk, and whether the system is dynamically cold or dynamically hot and turbulent. These constraints will help distinguish between gradual gas accretion and interaction driven scenarios for the origin of its spiral structure.
The discovery contributes to a growing body of evidence that the early Universe produced organised galaxies more rapidly than standard models predict. Instead of a landscape dominated only by clumpy, irregular systems, observations now reveal disk galaxies, and in this case a grand design spiral, within the first few billion years after the Big Bang. This implies that gas inflows, star formation, and dynamical processes can build large, stable structures on shorter timescales than had been assumed.
Such findings also affect how astronomers think about the timing of planet formation and the emergence of potentially habitable worlds. If galaxies like Alaknanda reach a mature, disk dominated state early, then the conditions needed to form planetary systems may appear sooner in cosmic history than previously expected. Alaknanda, described as the most distant disk dominated grand design spiral galaxy yet identified, is therefore an important marker for the pace of structure formation in the young Universe.
Research Report:A grand-design spiral galaxy 1.5 billion years after the Big Bang with JWST
Related Links
National Centre for Radio Astrophysics, Tata Institute of Fundamental Research
Stellar Chemistry, The Universe And All Within It
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