ESA: A new supercluster, seen by Planck and XMM-NewtonThe Universe is a hierarchy: stars and dark matter compose galaxies which in turn are the building blocks of clusters, which are aggregated into superclusters. Superclusters grew from tiny fluctuations in an almost completely smooth distribution of matter and energy produced by the Big Bang. But the origin of these tiny fluctuations is a profound mystery: an extremely important mystery, since the creation of these fluctuations resulted in the Universe we live in today. X-ray imaging is a good way to identify superclusters, since the enormous gravitational field generated by the typical supercluster traps unimaginable quantities of gas, which, as it falls down into the gravitational well of the supercluster, gains energy and emits energetic X-rays. But X-ray detectors are best at observing relatively nearby clusters, while astrophysicists are (of course) most interested in understanding distant clusters, those that existed shortly after the creation of the material Universe. A new observatory called Planck is helping astrophysicists find and catalog such newborn superclusters. Planck measures small deviations introduced on the Cosmic Microwave Background produced as CMB radiation scatters off hot cluster gas; this scattering slightly heats the CMB from its usual temperature of 2.7 degrees above absolute zero, and Planck can precisely measure this temperature deviation. Follow-up observations of the superclusters identified by Planck will allow astronomers to understand the Universal structure of superclusters and so constrain the density inhomogeneities imprinted on the Big Bang. The image above shows a new supercluster identified by Planck, along with followup observations of the hot gas in the supercluster obtained by the XMM-Newton X-ray observatory.
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