Source: TH
Subject: Science and Technology
Context: Indian astronomers have discovered Alaknanda, an implausibly old and well-formed spiral galaxy dating to just 1.5 billion years after the Big Bang, using JWST data.
About Alaknanda Galaxy:
What it is?
- Alaknanda is a distant, fully developed spiral galaxy with a rotating disk, two symmetric spiral arms, and a central bulge—features thought to take billions of years to assemble.
Discovered in: James Webb Space Telescope (JWST) public data.
- Identified during the UNCOVER survey.
Origin:
- Formed when the universe was only ~1.5 billion years old.
- Observed at redshift z ≈ 4, placing it among the earliest known spiral galaxies.
- Name inspired by the Alaknanda river; paired symbolically with the Milky Way (Mandakini).
Key features:
- Clear spiral morphology: Two well-defined arms persist after disk/bulge subtraction
- Active star formation: ~60 solar masses per year along the arms
- Stable rotating disk: Indicates early dynamical settling
- Photometrically robust: Multiple independent redshift estimates agree
Significance:
- Current simulations rarely produce such structured spirals so early.
- Suggests accelerated disk formation via cold gas accretion or early interactions/mergers.
