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James Webb Space Telescope's View of 800,000 Galaxies Paints a Detailed Picture of Dark Matter

Astronomers used the James Webb Space Telescope to create the most detailed dark‑matter map to date, covering a sky region 2.5 times the size of the full Moon in Sextans. By observing for roughly 255 hours with NIRCam as part of the COSMOS program, they measured weak gravitational lensing across about 800,000 galaxies. The resulting map contains roughly ten times more galaxies than ground‑based surveys and twice the galaxy count of the previous Hubble map, revealing the density of dark matter with unprecedented clarity. Complementary MIRI data helped refine galaxy distances, strengthening the analysis.