Astrophysicists from Masaryk University (MUNI) participated in research that detected intergalactic wind for the first time, as reported in the prestigious scientific journal Nature. Using the advanced Resolve spectrometer on board the Japanese XRISM satellite, the research analysed the X-ray spectrum of the centre of the Centaurus galaxy cluster. The study revealed that the galaxy NGC4696 is exposed to winds moving at 130 to 310 km/s, preventing the gas from cooling and inhibiting star formation. This discovery sheds new light on intergalactic weather and the role of black holes in galactic atmospheres.
MUNI physicists were part of the XRISM mission science team as “guest scientists” nominated by the European Space Agency (ESA). Their main contribution was the analysis of images from the Chandra X-ray satellite, which reveal interactions between the ejection of the black hole at the centre of the cluster and the surrounding gas.
The scientific community widely agrees that ordinary matter – made up of atoms – accounts for just 5% of the universe, with the rest consisting of mysterious dark matter and dark energy, about which little is known. Even within that 5%, only a small fraction forms planets, stars, and galaxies. The vast majority exists as a rarefied, hot material filling the space between galaxies.
This rarefied and hot “gas” can be observed in large galaxies and galaxy clusters using space-based X-ray telescopes. Astrophysicists often refer to it as the “galactic atmosphere”, a term coined after space observatories first detected its existence 50 years ago. Until now, scientists could measure its density, temperature, and pressure, but its movement – whether calm, turbulent, or windy – remained unknown. The X-Ray Imaging and Spectroscopy Mission (XRISM) satellite has now provided the first insights into this aspect of intergalactic weather in the Centaurus galaxy cluster.
The Centaurus galaxy cluster – located about 100 million light-years from Earth – was one of the first targets the XRISM satellite and its Resolve spectrometer focused on after launch. The Resolve instrument has about 30 times higher resolution than spectrometers on previous missions, making it particularly suited to measuring gas velocities with unprecedented precision. The observations revealed that the galaxy NGC4696, which lies at the centre of this cluster, is exposed to a wind blowing at speeds of 130 to 310 km/s. It turns out that this gas in the centre of the cluster has an oscillating motion that mixes the gas, preventing it from cooling and subsequently forming stars.
“Plasma ejections from the vicinity of black holes at the centres of galaxy clusters create cavities in the galactic atmospheres that are often larger than individual galaxies,” said Tomáš Plšek, PhD student in astrophysics at Masaryk University and co-author of the paper. “Thanks to the detection method I developed, we detected three generations of these cavities at the centre of this cluster, which allowed us to study the influence of the giant black hole on intergalactic weather. This observation suggests that the intergalactic wind blowing from previous collisions of galaxy clusters may prevent the transformation of intergalactic matter into stars and planets.”
