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Shogo Masaki of the Department of Physics at Nagoya University and Masataka Fukugita and Naoki Yoshida of the University of Tokyo’s Institute of Physics and Mathematics of the Universe (IMPU) collaborated in an experiment to create a computer simulation that would hopefully figure out the location of dark matter. In late January, their experiment was successful.
The term intergalactic refers to the physical space between galaxies where matter is hardly distributed. Scientists previously thought that intergalactic space comprised of nothing, being only empty, and that galaxies, in contrast, have the highest concentration of matter. Masaki, Fukugita, and Yoshida, however, have discovered that these intergalactic zones are packed with clumps of dark matter.
In addition, they also learned that galaxies do not have clear, defined edges; instead, they “have long outskirts of dark matter that extend to their nearby galaxies” according to IMPU’s press release. These “outskirts” contain much of the matter – and dark matter – in the universe.
The existence of dark matter was proposed by Swiss astronomer Fritz Zwicky in the 1930s. Since then, there have been numerous experiments around the globe involving dark matter. Dark matter’s nature is still enigmatic: it is an invisible, dense substance, and it cannot even be detected by instruments. Scientists do know that dark matter takes up about 23% of the Universe, with dark energy taking up 72% and the rest (planets and stars, for example) only 4%.
Furthermore, contrary to popular belief, dark matter is not random – it is uniform and organized. Masaki and his colleagues gathered recent observational data of 24 million galaxies from the Sloan Digital Sky Survey (SDSS) and created a large simulation of matter distribution. With their knowledge of the large density of dark matter, they used gravitational lensing to find the substance’s location.
Because dark matter is so dense, it causes space and light from stars, galaxies, and other light-emitting objects to bend, making these celestial objects appear bigger and brighter. With gravitational lensing, Masaki and his colleagues measured how the galaxies’ light was bent, allowing them to locate dark matter.
Dark matter remains as elusive as ever: although we have found exactly where dark matter is, we still do not know what it is, but scientists are closer than ever to understanding the mysterious substance’s nature. Masaki, Fukugita, and Yoshida have published a paper describing details of their experiment in The Astrophysical Journal. A PDF of the preprint version is found here.