b'17Postdoctoral fellow Xiaolong Du (left) and staff astronomer Andrew Benson (right) with student Turner Johnson, combined dark matter observations with theoretical modeling, using the phenomenon of gravitational lensing, to probe the mysteries of dark matter. Image courtesy Scott Rubel, Carnegie Institution for Science. . . they couldsuccessfully measure itwith theirnew systema boon to understandingthis enigmatic material.To isolate dark matter physics and to differentiateeffects from gravitational drag, tidal forces, and other among particle types, the researchers needed tointeractions. They ran the model tens of thousands look at masses below 10 8solar masses. They appliedof times to average results. They found that with 50 forward modelingwhich starts with causes tolenses it is possible to probe below 10 8solar masses calculate effectsusing changes in brightness ratiosand that if the mass of the dark matter particle is from the four images under different particle models.200,000 times lighter than a hydrogen atom, they They then applied the calculation to 50 mock lenses,could successfully measure it with their new systema which included complicated physics such as theboon to understanding this enigmatic material. Using gravitational lensing, the researchers could measure the distribution of matter across Halo cosmological distances. The measurements pointed to extra masssmall dark matter halos (left image). They could determine how many and where the halos are located. The image at right show a dark matter subhalo being pulled Galaxy apart by the tidal forces of the larger dark matter halo in which it orbits. The blue shows dark matter that has been pulled away from the center of mass by the tidal forces. The colored Subhalos points (blue, red, green, and yellow) show the subhalo where the dark matter is most dense, and the white shows the orbit that it followed.Images courtesy Xiaolong Du, Carnegie Institution for Science'