This process, called strong gravitational lensing, transforms galaxy clusters into colossal natural telescopes that give us a glimpse of distant cosmic objects that would normally be too faint to be visible. Light that would normally pass near a galaxy cluster instead bends toward and around it, producing intensified – and sometimes multiple – images of the background source. So when light passes by a mass, its path curves as well: a straight line in a curved space. Light always travels in a straight line, but space-time – the fabric of the universe – is curved by concentrations of mass within it. If dark matter is invisible, how do we know it exists? While dark matter doesn’t interact with normal matter in most cases, it does affect it gravitationally (which is how it was first discovered decades ago), so we can map its presence by looking at clusters of galaxies, the most massive structures in the universe. Madrid (Australian Telescope National Facility The rapid motion of its galaxies was the first clue that dark matter existed. This Hubble Space Telescope mosaic shows a portion of the immense Coma galaxy cluster - containing more than 1,000 galaxies - located 300 million light-years away. This Hubble Space Telescope mosaic shows a portion of the immense Coma galaxy cluster.

These surveys will yield new insight into the fundamental nature of dark matter, which will enable scientists to hone their searching techniques. Roman’s enormous surveys will provide a comprehensive look at the distribution of galaxies and galaxy clusters across the universe in the most detailed dark matter studies ever undertaken, thanks to dark matter’s gravitational effects.

We don’t even have a very good idea what the mass of dark matter particles might be, which makes it difficult to work out how best to search for them. There is currently a wide range of dark matter candidates. Ever since these discoveries, scientists have been trying to piece together the puzzle using sparse clues. Stars toward the edge of the galaxy move too fast to be held in by the galaxy’s luminous matter – there must be much more matter than we can see in these galaxies to hold the stars in orbit. Then in the 1970s, American astronomer Vera Rubin discovered the same type of problem in individual spiral galaxies. Scientists first suspected dark matter’s existence over 80 years ago when Swiss-American astronomer Fritz Zwicky observed that galaxies in the Coma cluster were moving so quickly they should have been flung away into space – yet they remained gravitationally bound to the cluster by unseen matter. This visualization shows how dark matter (blue-gray threads) provided the framework for normal matter (bright spots) to build up into large cosmic structures, like galaxies and galaxy clusters.

Roman will provide clarity by exploring the structure and distribution of both normal matter and dark matter across space and time. Scientists are trying to determine what dark matter is made of, but our current understanding has many gaps.

Roman Community Forum and Mailing List Signup.

Call for Community Input into the Definition of the Roman Space Telescope’s Core Community Surveys.

Roman Early-Definition Astrophysics Survey Assessment.

Roman space telescope wiki