Chandra Release - October 13, 2022

Visual Description: Abell 98 WHIM

This release features a composite image of Abell 98, a system of galaxy clusters about 1.4 billion light years from Earth. In the image, glowing and gleaming white specks -- mostly galaxies -- fill the blackness of space. Near the top and bottom of the image are clouds of blue gas, each with a glowing cluster of galaxies at its core. These two galaxy clusters are in the early stages of a collision.

 

The two large blue clouds of gas are X-ray emissions detected by the Chandra Observatory. Upon close inspection, a faint corridor of blue gas can be found bridging the space between the clusters. Scientists have proposed that this X-ray bridge between the clusters contains some of the unaccounted-for mass in the universe. Hidden in this bridge are gigantic strands, or filaments, of hot gas. This has been dubbed the “warm-hot intergalactic medium,” or WHIM.

 

The hotter gas in the bridge is likely from gas in the two clusters overlapping with each other. Another feature in the image is a faint shock wave. The labeled version of the primary image includes a curved, dotted red line under the blue cloud at the top. This shock wave line marks a decrease in the brightness and temperature of the X-rays between the blue gas clouds. It may be that this advancing shock wave is heating the gas in the WHIM filament as the clusters collide.