Via the Daily Mail in the U.K.:

A huge ‘bridge’ of invisible ‘dark matter’ has been detected holding two galaxy clusters, Abell 223 and Abell 222, together.

The filaments are thought to be a ‘glue’ that holds huge galaxy clusters together, but dark matter is extremely difficult to detect, as it does not emit any radiation.
Instead, the ‘bridge’ was detected by the gravitational ripples it caused in space, distorting the light from nearby stars as it arrived on Earth.

‘Dark matter’ is a theoretical – and controversial – substance which is undetectable by telescopes on earth, but thought by some scientists to account for up to 98% of the mass of the whole universe.

Dark matter is believed to act as a glue that binds galaxies together. Without it, the universe would not exist in its present form.

‘This is the first time a dark matter filament has been convincingly detected from its gravitational lensing effect,’ said astronomer Jörg Dietrich of the University Observatory Munich, in Germany in an interview with Space.com.

Read more: http://www.dailymail.co.uk/sciencetech/article-2169163/Cosmic-web-mysterious-dark-matter-detected-holding-galaxy-clusters-together.html#ixzz20B8vwNNv

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[Photo caption: The filament is made of dark matter, a mysterious substance thought to make up up to 98% of the universe, but which is extremely difficult to detect.]

Read more: http://www.dailymail.co.uk/sciencetech/article-2169163/Cosmic-web-mysterious-dark-matter-detected-holding-galaxy-clusters-together.html#ixzz20BB4YObU]