Faint Light Reveals the Shape of Invisible Dark Matter ⚡ экспресс
Scientists have discovered that diffuse light in galaxy clusters (intracluster light) traces the shape of invisible dark matter, like sparks from a campfire trace the gusts of an unseen wind. This gives astronomers a new way to 'see' dark matter. Isn't it amazing that the brightest clues can be hidden in the faintest details?
In galaxy clusters, invisible dark matter serves as the framework holding star systems together. Its shape is betrayed by a faint glow—stars ripped from galaxies by tidal forces. This stellar 'broth' fills the cluster like a liquid taking the shape of its container: it envelops the clumps of dark matter, creating a precise cast of their outlines. Astronomers measured the elongation of the light cloud and compared it to the shape of the dark halo: the direction of flattening matches to within ten degrees, and the contours themselves differ by only a few percent. Astonishingly, this glow is made of billions of stars—yet together they shine fainter than a large galaxy, less than one percent of its brightness. The method uses photometry—a precise measurement of brightness that reveals faint details. It provides a more reliable picture than previous estimates based on galaxy motions. Back in the 1930s, Fritz Zwicky suspected invisible mass in clusters; now its outlines can be read in the silent light.
🎯 Though billions of stars produce this light, altogether they shine at less than 1% the brightness of the cluster's central galaxy.