Distortion of light from distant galaxies by nearby galaxy cluster SDSS J0915+3826. This image by the NASA/ESA Hubble Space Telescope (HST) shows light from distant galaxies subject to gravitational lensing. This effect works when the gravitational influence of a massive object, such as the galaxy cluster in the centre of this image, is large enough to warp the surrounding space, causing nearby light to travel along distorted paths. The massive object is effectively turned into a giant magnifying glass, bending and amplifying the light travelling from more distant galaxies lying behind it. In this particular case, astronomers used the foreground galaxy cluster, SDSS J0915+3826, to study star formation in galaxies lying so far away that their light has taken up to 11.5 billion years to reach the HST.