Nearly a third of all galaxy clusters may have been previously unnoticed

Nearly a third of all galaxy clusters may have been previously unnoticed
In 1933, Fritz Zwicky, famous American astronomer of Swiss origin, arrived at the astonishing conclusion that even though galaxies are the signposts of galaxy clusters, their contribution to the total cluster mass is minuscule in comparison to a dominant dark matter component. Current estimates of a cluster total mass indicates that the contributions are roughly:
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