Roman Space Telescope to Unveil Dark Matter Secrets with Einsteins Gravitational Lensing

In 2027, the Nancy Grace Roman Space Telescope will embark on its scientific operations, utilizing a space-bending effect first predicted by Albert Einstein in 1916 to explore one of science's greatest mysteries: the nature of dark matter. This phenomenon, known as gravitational lensing, occurs when objects of great mass warp the fabric of space-time, causing light from background sources to be curved as it passes through these "dents" in the cosmos.

A new study suggests that the images created by the Roman Space Telescope during its vast cosmic surveys could contain around 160,000 gravitational lenses. The research team estimates that around 500 of these could be ideal for investigating dark matter, the universe's most mysterious "stuff."

The principal investigator of the research team, Tansu Daylan, explains that the ultimate goal is to determine what particle or particles constitute dark matter. While some properties of dark matter are known, scientists essentially have no idea what makes up this elusive substance. The Roman Space Telescope will help distinguish how dark matter is distributed on small scales and, hence, its particle nature.

Dark matter represents a significant puzzle for scientists because it makes up around 85% of the matter in the universe, yet they have little idea what it actually is. The lack of interaction with electromagnetic radiation makes it effectively invisible and unable to be composed of particles like electrons, protons, and neutrons that make up everyday matter.

To search for new particles that could account for dark matter, scientists have looked beyond the standard model of particle physics. However, dark matter can still curve light using another of the universe's four fundamental forces: gravity. General relativity states that all bodies with mass curve space-time to some extent, and light is then forced to follow this curve, allowing dark matter to play a role in gravitational lensing.

Gravitational lensing happens when light from a background source passes an object of great mass, like a galaxy. The curvature of this light depends on how close the light passes to the body of mass. This means that light from the same source can take paths of different lengths around a gravitational lens, arriving at the same telescope at different times.

The Roman Space Telescope will generate images around 200 times larger than those produced by the Hubble Space Telescope. Its 300-megapixel camera will allow researchers to gauge the bending of the background galaxies' light with such precision that it is akin to measuring the diameter of a human hair from the distance of more than two and a half American football fields or soccer pitches. This sensitivity will allow researchers to detect and characterize smaller, less massive dark matter structures.

Roman could help spot the sort of dark matter "clumps" that scientists propose came together in the early universe to build galaxies. Bryce Wedig, study team leader also of Washington University in St. Louis, notes that finding gravitational lenses and being able to detect clumps of dark matter in them is a game of tiny odds. With Roman, they can cast a wide net and expect to get lucky often. They won't see dark matter in the images—it's invisible—but they can measure its effects.

The team's research was published on June 5 in The Astrophysical Journal. With Roman's help, scientists will push the limits of what they can observe and use every gravitational lens detected to pin down the particle nature