Context:
In a significant breakthrough in astronomy and cosmology, Indian astronomers have discovered an unexpectedly old spiral galaxy, named Alaknanda, dating back to just 1.5 billion years after the Big Bang. The finding, made using the James Webb Space Telescope (JWST), challenges long-held theories of galaxy formation and evolution.
Key Highlights:
Discovery and Observation
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Alaknanda is the second farthest known spiral galaxy discovered so far.
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Detected by Indian astronomers using the James Webb Space Telescope (JWST).
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The galaxy was discovered serendipitously during a study on galaxy shapes in the early universe.
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Exists at a time when the universe was still in its early evolutionary phase.
Unusual Structural Features
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Exhibits a well-defined rotating disk with two prominent spiral arms.
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Such orderly spiral structures are considered rare in the early universe.
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Shows a high star-formation rate of nearly 60 solar masses per year, indicating intense stellar activity.
Why the Discovery Is Surprising
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Conventional models suggest spiral galaxies take several billion years to form stable disks.
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The presence of a mature spiral structure just 1.5 billion years after the Big Bang contradicts these models.
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Possible formation mechanisms include:
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Steady accretion of cold gas
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Merger with a smaller galaxy
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However, both mechanisms generally require longer time scales than observed.
Methodology Used
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Photometric analysis was employed to estimate:
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Redshift
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Stellar mass
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Star-formation history
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Results were corroborated using three independent redshift measurements, strengthening reliability.
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Spectroscopic observations are still required to:
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Confirm the spiral structure conclusively
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Identify the dominant formation mechanism
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Broader Significance
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Calls for re-evaluation of galaxy formation theories.
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Demonstrates the scientific potential of Indian astronomers in global research.
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Highlights the need for:
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Greater investment in domestic astronomical facilities
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Enhanced training programmes
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Stronger international collaborations
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Relevant Prelims Points:
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Issue: Early formation of a mature spiral galaxy.
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Causes (Possible):
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Rapid cold gas accretion
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Early galactic mergers
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Scientific Instruments:
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James Webb Space Telescope (JWST)
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Key Features:
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Spiral arms
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High star-formation rate
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Impact:
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Challenges standard cosmological timelines
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Improves understanding of early universe dynamics
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Relevant Mains Points:
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Key Concepts & Definitions:
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Redshift: Increase in wavelength of light due to cosmic expansion, used to measure distance.
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Photometric analysis: Measurement of brightness across wavelengths to infer physical properties.
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Spiral galaxy: Galaxy with a rotating disk, central bulge, and spiral arms.
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Science & Technology Linkages:
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Role of advanced telescopes in revising theoretical models.
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Importance of data-driven cosmology.
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Way Forward:
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Conduct spectroscopic follow-up studies.
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Increase Indian participation in global space missions.
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Strengthen astronomy education and research infrastructure.
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UPSC Relevance (GS-wise):
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GS Paper III – Science & Technology: Space science, cosmology, research and innovation.
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Prelims: Astronomy terminology, space missions, scientific discoveries.