Galaxy cluster, with older galaxies circled in yellow and younger in blue.
Astronomers have discovered the most massive galaxy cluster ever found, containing several hundred galaxies and a mind-boggling 800 trillion suns. Scientists at the South Pole can view the cluster as it appeared 7 billion years ago, when the universe was half its current age and before our solar system existed.
Despite its enormous size, the galaxy cluster ~ named SPT-CL J0546-5345 ~ was unseen until astronomers looked for distortions in the cosmic microwave background.
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