Record-Breaking Galaxy Cluster Confirms Dark Matter Universe
“But this new cluster is just 2.6 billion years old, and seems to be undergoing the very transition where a collection of galaxies falls into a bound structure for the first time, from a protocluster to a true galaxy cluster. This marks the first time astronomers have ever detected such an event: of the exact moment that a protocluster transitions to a true cluster. The fact that so many total galaxies (seventeen!) were discovered localized together at the same redshift (z=2.506) was a big hint, but the final piece of evidence came from the X-rays, where the diffuse emission engulfing the entire set of objects shows, beyond a shadow of a doubt, that this really is a galaxy cluster!”
There was once a time early on in the Universe where there were no stars, no galaxies and no clusters of galaxies at all. While stars and galaxies form very early on, after only tens or hundreds of millions of years, it takes billions of years for the first clusters to form. Yet even if we were to look back into the Universe’s past up to ten billion years, the clusters we see are already well-evolved and quiet. We had never seen a set of galaxies fall in and actively form a cluster before. We’d never seen the protocluster/cluster transition before. And we’d never found one from when the Universe was between two and three billion years old: when our dark matter theory predicts the first great clusters ought to form. Until, that is, now.