Weird clump in the early universe is piping hot and we don’t know why
A galaxy cluster in the early universe is 10 times hotter than it ought to be, which may reshape how we think these enormous structures formed
Space
A galaxy cluster in the early universe is 10 times hotter than it ought to be, which may reshape how we think these enormous structures formed
By Leah Crane
5 January 2026
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This galaxy cluster should be much, much colder than it is
Lingxiao Yuan
A young galaxy cluster in the early universe is defying our understanding of how these huge structures formed and evolved. The gas that fills this cluster, called SPT2349-56, is far hotter and more abundant than it should be, and researchers aren’t sure why.
Dazhi Zhou at the University of British Columbia in Canada and his colleagues observed the cluster using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile and found that towards its centre, the intracluster gas has a temperature of at least several tens of millions of degrees.
“The temperature of the surface of the sun is a few thousand degrees Celsius, so this entire area is hotter than the sun,” says Zhou. “From our conservative calculation, it is 5 to 10 times hotter than expected based on simulations – that is very surprising because this kind of hot gas was expected to exist only billions of years later.”