Dark matter affects how stars move within galaxies, how galaxies build up over time, and how everything in the universe is held together — but no existing tool has directly detected it. While dark matter does not reflect, absorb, or emit light, it can still be indirectly observed by telescopes.

To better characterize dark matter, astronomers look for its influence on the light they can observe. Dark matter possesses mass, therefore it can distort light traveling through the cosmos in a process known as gravitational lensing.

The Nancy Grace Roman Space Telescope, set to survey the sky following its launch, will turn up hundreds of gravitational lenses where a massive galaxy in the foreground magnifies and distorts light from the background galaxy into arcs and swoops. Researchers will use Roman’s data to measure tiny deviations in the repeated imagery of the background galaxies, which will help them measure the effects of dark matter on incredibly small scales and better pinpoint what it is.