Gravitational Lensing in Abell 2390
One way that astronomers can “see” dark matter is through gravitational lensing, a quirk of spacetime by which light is bent by the gravitational fields of massive objects. Here—in a close-up of the concentration of light from the previous image—you can see gravitational lensing occurring in the arc of a distant galaxy. Light that otherwise would appear as a straight line takes on an arc shape, as it is bent around massive objects. Though dark matter cannot be directly observed, gravitational lensing can hint at where dark matter resides, manipulating ordinary matter through its gravity.
