A seemingly impossible cluster of more than 30 galaxies crammed into a volume just 500,000 light-years across has been found in the universe just 1.4 billion years after the Big Bang — and with a temperature that breaks all the rules.
The discovery, by astronomers using Chile's Atacama Large Millimeter/submillimeter Array (ALMA), of the galaxy cluster labeled SPT2349-56 challenges our understanding of how quickly galaxies and galaxy clusters were able to form.
