Faint Light Reveals the Shape of Invisible Dark Matter ⚡ экспресс
It's been verified whether intracluster light (stars between galaxies) can indicate the shape of a dark matter halo. Comparing 3D and 2D shapes in the Hydrangea simulation showed: the axes of these components nearly coincide (deviation <10°), and the flattening differs on average by only 0.07 — dark matter is slightly rounder. This is more accurate than estimates based on the distribution of satellite galaxies, which are more elongated and less aligned. Thus, the diffuse stellar glow can indeed serve as a reliable marker of the shape of the dark scaffolding of clusters.
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.