Telescopes Unveil View Of Remote, Massive Galaxy Cluster

This image is a colour composite taken by ground-based and X-ray observatories showing the entire galaxy cluster surrounded by background and foreground galaxies. The blue colour in the center of the image represents the huge amount of hot gas that fills the space between the galaxies in the cluster. This gas - colored blue - cannot be seen in visible light, but glows in X-ray frequencies. Astronomers have measured its temperature at 300 million degrees Fahrenheit. The X-ray information was used to estimate the cluster's total mass.