Scientists have finally solved a long-standing mystery: why do galaxy clusters stay hot?
Thanks to a new discovery from the XRISM satellite, researchers now know that gas inside galaxy clusters moves like liquid in a shaken cup, keeping the clusters warm.
A Cosmic Mystery
Galaxy clusters are the largest structures in the universe, made up of hundreds or even thousands of galaxies. These clusters are surrounded by hot gas that emits X-rays.
However, scientists have been puzzled for years—this gas should be losing energy and cooling down over time, yet it stays hot. Until now, no one fully understood why.
The XRISM (X-ray Imaging and Spectroscopy Mission) satellite, launched by Japan’s space agency JAXA in 2023, recently observed the Centaurus Cluster, a massive group of galaxies that includes NGC 4696 at its center. Using a powerful spectrometer called Resolve, the satellite measured the speed of hot gas inside the cluster with incredible accuracy.
Researchers found that this gas is moving at speeds of 130 to 310 kilometers per second. This is the first direct proof of large-scale gas flows inside a galaxy cluster.
The ‘Sloshing’ Effect
Scientists compared their findings to advanced computer simulations and realized that these fast-moving gas flows are caused by collisions between galaxy clusters.
When clusters crash into each other, their gravitational forces create a “sloshing” motion, similar to how water sways in a tilted glass. This movement helps mix and transfer energy throughout the cluster, preventing the gas from cooling down.
This discovery provides the missing piece to the puzzle. Instead of cooling as expected, the sloshing effect keeps the cluster’s gas hot by constantly stirring and redistributing energy.
This breakthrough gives astronomers new insight into how galaxy clusters evolve and stay active. It also supports the idea that mergers and interactions between galaxy clusters play a crucial role in shaping the universe. The results of this study were recently published in the journal Nature.
With XRISM still in operation, scientists hope to uncover even more about the hidden processes happening in deep space. This is just the beginning of a new era in understanding how our universe changes and develops over time.
