Science Themes

Roman was conceived to address long-standing questions about dark energy, dark matter, and exoplanets.  However, Roman’s anticipated scientific impact is far greater, with transformational advances expected across all of astronomy. With a Hubble-sized mirror and equivalent resolution, a Wide Field Instrument (WFI) with a field of view more than 200 times that of Hubble's current IR camera, and survey speeds up to 1,000 times faster than Hubble, Roman will play a pivotal role in astrophysics in the 2020s and beyond.

The primary goal of the Roman mission is to maximize the scientific return from wide field near-infrared surveys across all of Astrophysics. Its near-infrared sensitivity, high-resolution imaging and spectroscopy, expansive field of view, precise pointing control, and high survey speed will enable the collection of large samples that will benefit many fields. Roman is expected to observe thousands of planetary bodies in the Milky Way and small bodies in our own Solar System, millions of galaxies, and billions of stars in the Milky Way and neighboring galaxies. Such “big data” will uniquely address important questions on many topics, including planetary science, stellar populations, galaxy evolution, and cosmology.

Roman’s WFI observing program will comprise a mix of Core Community Surveys and General Astrophysics Surveys, both of which will enable multiple scientific investigations. While the Core Community Surveys are the mechanism by which Roman will address its goals in cosmology and exoplanet science, described below, their expected science return is much greater. These Core Community Surveys are currently being optimized to enable a breadth of science through a community-led process. All of Roman’s data will be non-proprietary, with General Investigator opportunities for funding archival programs available for all science areas. 

Dark Energy

The Roman Space Telescope will measure the equation of state of dark energy and its time evolution, helping to determine whether it is a cosmological constant. The High Latitude Wide-Area Survey (HLWAS) will enable weak lensing shape and photometric redshift measurements of hundreds of millions of galaxies, which will yield precise estimates of distances and matter clustering through measurements of cosmic shear, galaxy-galaxy lensing, and the abundance and mass profiles of galaxy clusters. Spectroscopic measurements over the same area will enable the determination of millions of redshifts for galaxies of redshifts between 1 and 3, thus allowing a measurement the growth of structure via redshift-space distortions, and the constraint of the scale of baryon acoustic oscillations to 0.3%. At the same time, the High Latitude Time Domain Survey (HLTDS) will enable the discovery and measurement of precise distances to thousands of Type Ia supernovae up to redshift 2.

Dark Matter

Roman will be used to investigate dark matter in a number of ways, including the study of weak gravitational lensing effects. Weak lensing tracks how the shape of distant galaxies is warped by small clumps of dark matter.

Additionally, the large footprint of the Roman Wide Field Instrument (WFI) will allow an inventory of both normal matter and dark matter in hundreds of millions of galaxies. Such observations will be used to understand how dark matter has driven the formation and evolution of stars and galaxies as a function of cosmic time. If galaxy formation is observed very early in cosmic history, it could signal that dark matter is made of heavy, sluggish particles that tend to clump together quickly. On the other hand, if the dark matter clumps grow more slowly and the large-scale structure is established over a longer time scale, it would indicate that dark matter is made up of lighter, faster-moving particles.

Roman’s observations will help reconstruct the history of galaxies and clusters formation under the influence of dark matter, which, in turn, will help scientists narrow down candidates for dark matter particles, pointing the way for direct detection in experiments on Earth.

Exoplanets

Roman will use time-series microlensing imaging observations of Milky Way Bulge stars to determine the distribution of exoplanets down to sub-Earth masses in a wide range of orbital radii, including planets in habitable zones, planets in the outer regions of planetary systems, and free-floating planets.

The Coronographic Instrument on Roman will provide a crucial technology demonstration for possible future missions aimed at detecting signs of life in the atmospheres of Earth-like exoplanets. It will also be capable of directly imaging planets similar to those in the Solar System, measuring for the first time the photometric properties of the so-called Sub-Neptune or and Super-Earth planets — objects that the Kepler missions have shown to be the most common planets in our galaxy, but with no analog in our own solar system.