HEAPOW: The Bones of the Universe (2010 Jan 18)
The XMM-LSS 11 deg2 MosaicThe word "cosmos" is derived from the Greek kosmos, meaning an "orderly, harmonious arrangement", but also suggesting ornamental. The word "harmony" is derived from the word "harmos", meaning "joint" or "shoulder". Thus our cosmos can be thought of as a collection of brightly colored ornaments fitting together like the bones in a body. The bones that give structure to our Universe are clusters of galaxies. To understand the underlying order and structure of this Universal body, we need to study the bones. And of course the best way to do that is to take an X-ray. Since 2003 astronomers, using the XMM-Newton X-ray telescope, have been doing exactly that. The XMM Large Scale Survey, shown above, is a mosaic of X-ray images over 11 square degrees on the sky (about the size of 22 full moons) at 1000 times the sensitivity of the previous best X-ray cluster survey. Colors in the mosaic represent X-ray energy: red for low energy X-rays, green for medium and blue for high energy X-rays. Of the 7000 sources detected in this mosaic, about 200 are clusters of galaxies, some of which are shown by the white circles in the image. Red boxes show particularly interesting sources, seen more closely in the inset images on the right.
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