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yesterday

Webb Delivers Sharpest Dark-Matter Map, Revealing the Universe’s Hidden Scaffold

Astronomers used Webb’s weak‑lensing measurements to reconstruct a high‑clarity mass map that confirms dark matter underpins the cosmic web.

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Scientists used the Victor M. Blanco Telescope in Chile to observe the expansion rate of the universe in four different ways.
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Artist's rendering of James Webb Space Telescope in space near Earth, in this image released on September 19, 2023. NASA/dima_zel/Handout via REUTERS THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY

Overview

  • The Nature Astronomy study reconstructs the most detailed contiguous mass map of the COSMOS field, at roughly twice Hubble’s resolution.
  • Webb imaged the Sextans region for about 255 hours, identifying nearly 800,000 galaxies and enabling shape measurements for about 250,000 background sources used for weak‑lensing analysis.
  • The map reveals finer clumps, filaments and underdense regions where dark matter tracks visible structures, supporting the standard Lambda‑CDM framework.
  • Mid‑infrared data from MIRI improved distance estimates and added dust‑obscured galaxies, increasing the density of background tracers and the map’s clarity.
  • The COSMOS‑Webb field becomes a high‑resolution reference as ESA’s Euclid and NASA’s Nancy Grace Roman prepare much larger, lower‑resolution dark‑matter surveys.