Home > Astronomy, Astrophysics, Dark Energy & Matter, Galaxies, General Astronomy > Intergalactic Space Is Filled with Dark Matter

Intergalactic Space Is Filled with Dark Matter


It is well known that there is a large amount of unseen matter called “dark matter” in the universe. It constitutes about 22 percent of the present-day universe while ordinary matter constitutes only 4.5 percent. An important question still remains – Where is most of the dark matter in the universe ?

Einstein’s theory of general relativity predicts that a light ray passing through near a massive object such as a galaxy is bent by the effect called “gravitational lensing”. For example, the effect causes the image of a distant galaxy to be deformed and brightened by an intervening galaxy. However the effect itself is very small and so cannot be easily detected for a single galaxy. Only recently, images of millions of galaxies from Sloan Digital Sky Survey (SDSS) made it possible to derive an averaged mass distribution around the galaxies. Earlier in 2010, an international research group led by Brice Menard then at University Toronto and Masataka Fukugita at IPMU used twenty four millions galaxy images from SDSS and successfully detected gravitational lensing effect caused by dark matter around the galaxies. From the result, they determined the projected matter density distribution over a distance of a hundred million light years from the center of the galaxies.

Full Story: http://www.ipmu.jp/node/1222

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