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James Webb Space Telescope Challenges Cosmic Understanding
Context:
- JWST has captured images of fully developed, adult-sized galaxies from the early Universe, contrary to expectations of seeing smaller, newborn galaxies.
- Discrepancies in the Expansion Rate: Scientists have used two primary methods to measure this expansion:
- Early Universe Measurements: These rely on observations of relic radiation from the early Universe, known as the cosmic microwave background (CMB).
- This radiation, which has cooled to a microwave hum, provides a snapshot of the Universe’s conditions shortly after the Big Bang.
- Local Measurements: These use observations of celestial objects, such as variable stars, to determine distances and infer the expansion rate.
- JWST’s data shows a faster expansion rate compared to measurements from early Universe methods, increasing the existing 10% discrepancy between the two methods.
- The discrepancy raises questions about the reliability of these methods and the accuracy of current cosmological models.
JWST Discoveries and Challenges:
- It was intended to observe and analyse “toddler galaxies” — those that formed when the Universe was relatively young.
- It has revealed galaxies at the dawn of the Universe that are unexpectedly well-developed, with billions of stars. This is akin to finding “adults in a kindergarten,” which challenges previous models of galaxy formation.
- Some of these galaxies date back to when the Universe was only a few hundred million years old, yet they appear to be mature, containing numerous bright stars.
- This suggests that star formation occurred much earlier and more rapidly than previously believed.
Implications:
- These observations could imply either a need to revise our understanding of galaxy formation or that there may be previously unconsidered astrophysical processes at work.
- They have amplified existing discrepancies between the rates of expansion inferred from early Universe observations and those from local measurements, fueling further debate and research.
JWST’s Launch and Capabilities
- Launch Date: December 25, 2021, from ESA’s launch site at Kourou in French Guiana, aboard an Arianespace Ariane 5 rocket.
- Destination: Sun-Earth Lagrange point 2 (L2), arrived in January 2022.
- Mirror Size: Five times larger than the Hubble Space Telescope.
- It is the result of a remarkable international collaboration involving NASA, the European Space Agency (ESA), and the Canadian Space Agency.