Packs of densely populated stars can function like giant gravity-powered magnifying glasses. And this image, taken by the Hubble telescope, shows how they do it: by warping the very fabric of space and time.
In galaxy clusters, the largest known structures in the Universe, stars are so densely packed that the force of their gravity bends space itself. Sometimes, as in the case of galaxy cluster Abell S1077, the warping of the fabric of space-time creates a curvature in space similar to that of a magnifying glass.
This magnifying effect allows us to spot objects that could never be found when gazing upon the heavens from Earth. Objects that would be, for instance, hidden behind others. Take another look at the starscape above. Those stretched arcs of light, those which almost look like scratches upon a lens, are actually the warped images of hidden galaxies from behind galaxy cluster Abell S1077.
With the aid of gravitational forces from these space-time magnifying lenses, scientists have been able to detect some of the most ancient light in the universe. Like that from galaxy MACS0647-JD, the light from which has taken 13.3 billion years to reach human eyes.