Exoplanets are incredibly dim and distant, making them almost invisible even to the most powerful telescopes. For this reason, the vast majority of the thousands of exoplanets discovered so far have been detected indirectly, through the subtle effects they have on their host stars. Astronomers observe tiny dips in starlight as a planet passes in front of its star or measure small stellar wobbles caused by a planet’s gravitational pull.
Today, however, recent technological advances are opening a new frontier: the ability to take direct images of exoplanets.
Planets are typically billions of times fainter than the stars they orbit, and their light is easily overwhelmed by stellar glare. To overcome this challenge, astronomers use specialized instruments such as coronagraphs or starshades, which block out the star’s light and allow the much fainter planets nearby to become visible. This direct imaging technique works best for planetary systems relatively close to Earth, where planets appear brighter and are easier to resolve.
The upcoming Nancy Grace Roman Space Telescope (Roman) will play a crucial role in advancing this technology. Equipped with a state of the art Coronagraph Instrument, Roman will demonstrate how to photograph planets and dusty disks around nearby stars with a level of detail up to a thousand times greater than what current observatories can achieve.
Although Roman is primarily designed as an infrared telescope, its Coronagraph Instrument will enable imaging in visible light from space. Observing from above Earth’s atmosphere eliminates atmospheric distortion, allowing astronomers to detect smaller, older, and colder planets than are typically revealed through direct imaging from the ground.
By capturing images of Jupiter-like planets orbiting other stars, so called “Jupiter analogs”—Roman will bring us significantly closer to one of astronomy’s greatest goals: directly imaging Earth-like worlds. Through missions like Roman, we are moving steadily toward a future where distant planetary systems are no longer just detected, but truly seen.