Researchers in Japan reckon they've pinpointed some of the missing dark matter that should be all over the universe. It turns out it's, uh, all over the universe – specifically in a massive web woven far out beyond the observable edge of each galaxy.So why was it so hard to find? Everything you touch, feel, smell… in fact everything you have ever (knowingly) been in contact with is made of matter, constituting less than 5% of the mass in our universe. So what about the other 95%? A quarter of this is dark matter (the rest is dark energy)– infamously hard to detect as it does not give out/reflect any electromagnetic radiation.Until now scientists were unsure where in the universe dark matter might be lurking, despite generally agreeing that it exists. They are pretty confident about its existence because the mass of galaxies calculated by observing all the stars, clouds of gas and dust we see spiraling around isn't heavy enough compared to the expected mass from measurements of the gravitational effects around galaxies. It is this mysterious missing mass that is attributed to dark matter – which can't be seen but must be there if we have anything about gravity right.In 2010, the Sloan Digital Sky Survey took images of millions of galaxies showing the gravitational effects of dark matter around the edge of galaxies; the edge being more than 100 million light years from the center of the galaxy. Now, using large computer simulations, physicists at the Institute for Physics and Mathematics of the Universe and Nagoya University have shown that galaxies actually have extensive outskirts of dark matter, reaching far into what was thought to be empty space, way beyond where any stars exist.It all fits together perfectly, with the amount of dark matter calculated to be sitting on the outskirts of galaxies in line with the mass of missing matter in the universe. Outer space, it turns out, isn't so empty after all.
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