The effects of the Universe’s large-scale structure on the light from distant galaxies

This illustration shows the bent paths of light from distant galaxies, caused by weak gravitational lensing from the Universe’s large-scale structure, or ‘cosmic web’. The galaxies’ true shapes become warped as the light from them travels and bends past the galaxies and galaxy clusters of the cosmic web on its way to us. By the time the light is observed, the galaxies’ observed shapes and positions have changed (represented by the pairs of galaxies to the right). The effect is highly exaggerated in this illustration, and studies of weak lensing distortions used to measure how mass is distributed in the Universe typically require measurements of millions of galaxies. Rubin Observatory’s Legacy Survey of Space and Time (LSST) will observe billions of galaxies and enable more precise weak lensing measurements than have been possible before.

Alt Text: An illustration of the path that light from distant galaxies might take through the cosmic web. The background is a dark blue with criss-crossing light blue filaments made of tiny dots, resembling wisps of smoke or strings of a cobweb. Three bright teal squiggly lines spider out toward the right from three small illustrated galaxies slightly left of center, representing a squiggly path that light might take. The squiggly lines end at a pair of illustrated galaxies, one teal and one white. The teal version shows the true shape and position of the galaxy as it would have been seen without weak gravitational lensing effects. The white version represents the galaxy’s observed shape and position, slightly elongated and offset compared to the teal.