By studying how light is distorted by galaxy clusters, astronomers have been able to create a map of dark matter in the universe.Ī vast majority of the astronomical community today accepts that dark matter exists. The phenomenon is called gravitational lensing. Famous physicist Albert Einstein showed in the early 20th century that massive objects in the universe bend and distort light due to the force of their gravity. The force of gravity doesn't only affect the orbits of stars in galaxies but also the trajectory of light. On the other hand, since 2018 astronomers have found several galaxies that seem to lack dark matter altogether. In 2016, a team led by Van Dokkum found a galaxy called Dragonfly 44, which seems to be composed almost entirely of dark matter. Clusters of galaxies would fly apart if the only mass they contained was the mass visible to conventional astronomical measurements.ĭifferent galaxies seem to contain different amounts of dark matter. Studies of gas within elliptical galaxies also indicated a need for more mass than found in visible objects. Instead, they found the stars in both locations traveled at the same velocity, indicating the galaxies contained more mass than could be seen. "They don't care what form the matter is, they just tell you that it's there."Īstronomers examining spiral galaxies in the 1970s expected to see material in the center moving faster than at the outer edges. "Motions of the stars tell you how much matter there is," Pieter van Dokkum, a researcher at Yale University, said in a statement (opens in new tab). Since the 1920s, astronomers have hypothesized that the universe must contain more matter than we can see because the gravitational forces that seem to be at play in the universe simply appear stronger than the visible matter alone would account for. Related: Image Gallery: Dark matter across the universeīut if we cannot see dark matter, how do we know it exists? The answer is gravity, the force exerted by objects made of matter that is proportional to their mass. Unlike dark matter, physicists can actually manufacture anti-matter in their laboratories. Because we live in a universe made of matter, it is obvious that there is not that much antimatter around, otherwise there would be nothing left. When antiparticles meet particles, an explosion ensues that leads to the two types of matter cancelling each other out. These particles are called antiprotons and positrons (or antielectrons). Antimatter consists of particles that are essentially the same as visible matter particles but with opposite electrical charges. There is also such a thing as antimatter, which is not the same as dark matter. The smaller neutral axion and the uncharged photinos - both theoretical particles - are also potential placeholders for dark matter. "One of the outstanding questions is whether there is a pattern to the fractions that go into each neutrino species," Tyce DeYoung, an associate professor of physics and astronomy at Michigan State University and a collaborator on the IceCube neutrino observatory in Antarctica, told. The sterile neutrino would only interact with regular matter through gravity. There are three known types of neutrinos a fourth, the sterile neutrino, is proposed as a dark matter candidate.
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