When Clusters Collide Things Get Hot

Oct 21, 2022 | Daily Space, Galaxies

When Clusters Collide Things Get Hot
IMAGE: This image features Abell 98, a system of galaxy clusters that includes a pair in the early stages of a collision. Astronomers have used data from NASA’s Chandra X-ray Observatory (shown as blue and purple with optical data from the WIYN telescope on Kitt Peak in Arizona appearing white and red) to identify key structures and look for “missing” matter in the Universe. CREDIT: X-ray: NASA/CXC/CfA/A. Sarkar; Optical: NSF/NOIRLab/WIYN


Gas really lurks in a lot of different places. As we search our universe for missing matter, we aren’t just looking for dark matter, we’re also looking for gas and dust. And that stuff is really hard to find sometimes – at least in the colors of light we see with our eyes. That means we need to go looking for it in other ways. The Chandra X-Ray Observatory is just the tool researchers need.

A newly released image of the merging galaxy cluster Abell 98 reveals a faintly shining network of hot gas connecting the two cluster cores. This gas is termed the “warm-hot intergalactic medium” or WHIM by the researchers.

And by warm, they mean ten thousand to ten million Kelvin!

This network of gas is formed by a shockwave that is created by the clusters’ collision. According to team researcher Scott Randall: We think this shock wave is an important discovery because our models have predicted such features should be there, but we haven’t seen one until now. They’re a key part of the early collision process that will eventually lead to a merger of the clusters.

That, and they are made of the missing gas we needed to find. The team estimates there is 400 billion times the mass of the Sun connecting these galaxies.

More Information

CXO image release

CXO press release

Discovery of a Premerger Shock in an Intercluster Filament in Abell 98,” Arnab Sarkar et al., 2022 August 17, The Astrophysical Journal Letters

Suzaku Observations of the Cluster Outskirts and Intercluster Filament in the Triple Merger Cluster A98,” Gabriella E. Alvarez et al., 2022 October 13, The Astrophysical Journal

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