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For 350 million years, four clusters of galaxies have been staging a titanic collision. Many of the galaxies have been hurled onto new paths, or they’ve sideswiped each other, stirring up their stars and triggering the birth of new stars. Vast clouds of gas in the clusters have slammed together, heating them to millions of degrees. And through it all, the dark matter in the clusters has sailed right on through.
Collectively, these clusters are known as Pandora’s Cluster. It’s the first target for Frontier Fields — a project that combines the abilities of the Hubble, Spitzer, and Chandra space telescopes to study such massive clusters in detail.
The telescopes see the clusters at visible, infrared, and X-ray wavelengths. The combination helps astronomers measure temperatures, masses, and other traits.
The gravity of the massive cluster acts as a lens. It magnifies the light of galaxies beyond the cluster, allowing astronomers to see galaxies that formed not long after the Big Bang.
Pandora’s Cluster is about four billion light-years away, so we see it as it looked four billion years ago. It contains hundreds of individual galaxies. But most of its mass is in the form of dark matter, which produces no energy but exerts a gravitational pull on the visible matter around it. The observations are allowing astronomers to map the dark matter in detail — providing a good view of the invisible parts of a giant galactic pileup.
Script by Damond Benningfield, Copyright 2015