Only one billion years after the Big Bang, clusters of galaxies were already forming. This discovery pushes back the age of the youngest known galaxy cluster by a third, and shows that the largest astronomical objects in the Universe had already begun to form in one of the earliest epochs of the Universe that astronomers have been able to observe.

This work was conducted by researchers from the University of Tokyo, the National Astronomical Observatory of Japan, and elsewhere using the Subaru telescope.

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More info: Subaru telescope web page