Chandra Observation of 3 clusters
Credit: NASA/CXC/IoA/S.Allen et al.

Darkness Visible

Clusters of galaxies are the largest gravitationally bound objects in the Universe. Gas between the galaxies in these clusters emit X-rays, so that X-ray images are a good way to study these objects. A recent study of the X-ray emission from a carefully chosen selection of galaxy clusters by the Chandra X-ray observatory has revealed a startling thing: it appears that the the expansion of the universe stopped decelerating about 6 billion years ago, and began to accelerate. Scientists have determined this by studying the relation between the hot gas revealed by the X-ray emission detected by Chandra, and the dark matter which holds the hot gas in place.

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Each week the HEASARC brings you new, exciting and beautiful images from X-ray and Gamma ray astronomy. Check back each week and be sure to check out the HEAPOW archive!

Page Author: Dr. Michael F. Corcoran
Last modified Friday, 20-Apr-2012 15:23:12 EDT