Johan Richard

A massive galaxy cluster acts as a giant lens. Its gravity warps the fabric of space, and the light of distant objects, bending around this curvature, is amplified and split into multiple images.

Thanks to gravitational lens — an effect predicted by Fritz Zwicky, where a galaxy cluster acts like a magnifying glass — the James Webb Space Telescope spotted two red dots in a galaxy 800 million years after the Big Bang.

Light from a distant galaxy travels toward us for billions of years, but along the way it can run into a massive galaxy cluster. Its gravity acts like curved glass: it bends the path of rays, so instead of one image, we see several — sometimes arcs, sometimes points.