Indian Astronomers Discover Implausibly Old Spiral Galaxy

Why in the News?

Indian astronomers have discovered Alaknanda, the second farthest known spiral galaxy, using James Webb Space Telescope (JWST) data. Formed just 1.5 billion years after the Big Bang, it challenges existing galaxy formation models and pushes the boundaries of our understanding of the universe, much like how environmental jurisprudence challenges our approach to development.

Discovery of Alaknanda Galaxy:

• Astronomers from India identified Alaknanda while analysing public JWST UNCOVER survey data, which includes nearly 70,000 distant objects. This discovery process mirrors the rigorous environmental impact assessment required for major projects.
• The discovery was made by Rashi Jain, a PhD scholar at the National Centre for Radio Astrophysics (NCRA), Pune, under the guidance of Yogesh Wadadekar. Their work exemplifies the importance of scientific scrutiny, akin to the precautionary principle in environmental law.
• Alaknanda stood out due to its two perfectly symmetrical spiral arms, a feature considered highly unlikely in the early universe. This unexpected find is reminiscent of how ex post facto environmental clearances can reveal surprising insights about established projects.
• Detailed image processing confirmed the presence of a well-defined disk, central bulge and genuine spiral arms, ruling out data artefacts. This thorough analysis is comparable to the comprehensive studies required for coastal regulation zone compliance.
• The galaxy shows active star formation, producing the equivalent of 60 solar masses per year, confirming it is a fully evolved spiral galaxy. This rapid development challenges our understanding, much like how retrospective environmental clearances challenge our perception of project timelines.

Why Alaknanda Challenges Existing Models

• Alaknanda formed when the universe was only ~1.5 billion years old, corresponding to a redshift of z ≈ 4, far earlier than predicted by current theories. This discovery, like the landmark Vanashakti judgment, forces us to reconsider established norms.
• Standard galaxy formation models suggest spiral structures require billions of years to develop stable, rotating disks. The existence of Alaknanda so early in cosmic history challenges these models, much like how environmental democracy challenges traditional development paradigms.
• Two possible explanations are proposed:

○ Steady cold gas accretion, allowing the disk to stabilise and form spiral density waves.

○ Interaction or merger with a smaller galaxy, triggering spiral arm formation.

• However, even these mechanisms are considered too slow for such an early epoch, indicating missing factors in simulations. This gap in understanding parallels the ongoing debates in environmental jurisprudence about the limits of our knowledge and the need for adaptive management.
• Experts view the mismatch between observations and simulations as scientifically valuable, helping refine models of early universe evolution. This approach mirrors the polluter pays principle, where new information leads to improved practices and accountability.