XMM X-ray observation of the cosmic web
Credit: ESA/ XMM-Newton/ EPIC/ ESO (J. Dietrich)/ SRON (N. Werner)/ MPE (A. Finoguenov)


Scientists believe only about 5% of the Universe is made of normal stuff. Scientists call this normal stuff baryonic matter, the type that's familiar to us, made of protons and neutrons. The rest of the Universe is dark stuff, either dark energy or dark matter. But the normal stuff is mysterious too, since there doesn't seem to be enough of it, if you account for all the normal stuff that's easy to see around us, mostly stars, galaxies and gas clouds. Astronomers have only directly seen about half of all the normal baryonic matter that's believed to exist. Where's the rest of it? It may be in hot gas associated with the enormous web left behind by the formation of the structure in the Universe. A new observation with the XMM-Newton X-ray observatory may have actually seen a piece of this web. XMM-Newton observations of two clusters of galaxies called Abell 222 and Abell 223 revealed a bridge of hot gas extending from one cluster to the other. The image above shows an optical image by the Subaru telescope of these two clusters, with the bridge of hot gas superimposed. This bridge was only detectable because it happens to be located along the line of sight to earth, which concentrates the emission. How much else is out there?

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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 15:23:10 EDT