Nasa’s James Webb Space Telescope has produced one of the most detailed maps yet of dark matter by observing how its gravity subtly distorts light from distant galaxies, scientists said, drawing on one of the longest deep-space observations ever conducted by the observatory.
Using its Near-Infrared Camera (NIRCam), Webb spent about 255 hours observing a region of sky in the constellation Sextans as part of the Cosmic Evolution Survey (COSMOS). The surveyed area spans roughly 0.54 square degrees, or about two and a half times the apparent size of the Full Moon, and contains close to 800,000 galaxies. Researchers combined this data with a dark matter overlay derived from gravitational effects seen in the images.
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Dark matter itself cannot be seen directly because it does not emit or reflect light, but its presence can be inferred through gravitational lensing, a process in which mass bends the path of light traveling through space-time. In this study, scientists relied on weak gravitational lensing, which produces subtle distortions that become measurable only when large numbers of galaxies are analyzed together.
The resulting map depicts regions of higher dark matter density in blue, with brighter shades indicating stronger concentrations. According to the original article, “Webb’s map reveals new clumps of dark matter, as it contains about twice as many galaxies as Hubble’s map,” highlighting the telescope’s improved sensitivity and resolution compared with earlier observations made by the Hubble Space Telescope in 2007.
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The COSMOS project also incorporates data from several other observatories, allowing astronomers to compare different wavelengths and perspectives. Scientists say the combined datasets are helping to refine models of how galaxies form and evolve, and how dark matter shapes the large-scale structure of the universe over cosmic time.