Photo: MPIfR/N.Sulzenauer/ALMA
Scientists discover impossibly hot galaxy cluster just 1.4 billion years after the Big Bang
Astronomers have identified a giant galaxy cluster that challenges current models of cosmic evolution, Science Alert reports. The object, known as SPT2349-56, appeared only 1.4 billion years after the Big Bang and has a temperature far higher than expected. According to existing theories, gravitational heating of galaxy clusters is a slow process, requiring billions of years to reach the levels observed in SPT2349-56.
“We did not expect to see such a hot cluster atmosphere so early in cosmic history. At first, I was skeptical because the signal was too strong to be real. But after months of verification, we confirmed that this gas is at least five times hotter than expected — even hotter and more energetic than what we find in many modern clusters,” said astrophysics graduate student Dazhi Zhou of the University of British Columbia, Canada.
SPT2349-56 was first spotted in 2010 using a telescope at the South Pole. Subsequent observations in 2018 revealed that it contains over 30 galaxies, whose stars are forming at a rate 1,000 times faster than in the Milky Way. The galaxies are rapidly moving toward one another.
Galaxy clusters are regions of space where gravity strengthens as galaxies attract each other. This gravitational pull compresses and accelerates gas within the cluster, increasing its energy. SPT2349-56 is an extreme early-universe example, both in terms of size and star formation, and prior measurements showed significant molecular gas between its galaxies.
“Understanding galaxy clusters is key to understanding the largest galaxies in the universe. These massive galaxies mostly reside in clusters, and their evolution is heavily influenced by the intense cluster environment during formation, including the intracluster medium,” explained astrophysicist Scott Chapman of Dalhousie University, formerly with the National Research Council of Canada.
Analysis of ALMA telescope data revealed a clear thermal signature from hot electrons exceeding 10 million Kelvin. While astronomers hoped to detect an early hot intracluster medium, the signal far exceeded expectations.
Current models indicate that gravity alone cannot account for such high temperatures. Researchers suggest that additional energy may come from powerful jets from at least three supermassive black holes within SPT2349-56.
