Astronomers have used a principle first proposed by Einstein over 100 years ago to map the distribution of dark matter in unprecedented detail. The team’s method managed to reveal the presence of dark matter ‘clumps’ between galaxies, showing how this mysterious substance is distributed on smaller scales. Fluctuations in the observed dark matter, identified between a distant quasar and a galaxy between that quasar and Earth, could help constrain the properties of the elusive substance.
Dark matter is troubling for scientists because, despite the fact it makes up about 85 per cent of our universe, it’s effectively invisible. This is because dark matter either doesn’t interact with any electromagnetic radiation, including visible light, or does so incredibly weakly. This means the particles that make up dark matter – whatever they are – cannot be atoms composed of electrons, protons and neutrons. These are the baryons that form the everyday matter that makes up stars, planets, our bodies and everything we see around us. It’s this puzzle that has prompted an intense search for dark matter particles. Thus far, the only way scientists can infer the presence of dark matter is by looking at the effect it has on ‘normal’ matter via gravity.
We’ve discovered that if galaxies weren’t mostly made up of dark matter, their contents would quickly fly apart as they are rotating too rapidly to be held together by the gravity of the visible matter within them. Not only are galaxies believed to be enveloped by halos of dark matter to prevent such a catastrophe, but some dark matter models also suggest there should be clumps of dark matter inside galaxies as well as filling the space between them.
A team of researchers from Japan, led by Kindai University’s Kaiki Taro Inoue, set out to use the Atacama Large Millimeter/ submillimeter Array (ALMA) to better understand the distribution of dark matter around a distant, massive galaxy and find clumps of the mysterious matter in intergalactic space. To do this, they observed light from a quasar called MG J0414+0534, located 11 billion light years from Earth, by using an effect called gravitational lensing. Gravitational lensing is a concept that first emerged from Einstein’s theory of general relativity, which was published in 1915. This concept differed radically from Newton’s theory of gravity because it re-imagined the fabric of space and time – united as fourdimensional space-time – as a dynamic element of the universe, not just a static stage upon which cosmic events play out.
Einstein envisioned objects with mass as causing curvature, or a ‘warp’, in the fabric of space-time. The greater the mass, the more extreme th
