When NASA's Nancy Grace Roman Space Telescope launches as early as the end of next month, it will attempt one of astronomy's most precise disappearing acts[reference:88]. The telescope will carry the first space-bound "active" coronagraph — an instrument that effectively erases most of the light from a star during photography[reference:89].
The technology will allow astronomers to take the first pictures of planets orbiting other stars that are similar to those in our solar system. Ultimately, it could pave the way for a future mission that could snap the first photos of Earth-like worlds[reference:90].
"I hope it's remembered for it being that critical stepping stone for … finding Earth 2.0," says Brandon Creager, the instrument's lead mechanical engineer at NASA's Jet Propulsion Laboratory[reference:91].
How the Active Coronagraph Works
Coronagraphs in space aren't new. But earlier incarnations — such as those on Hubble and the James Webb Space Telescope — use stationary systems to block a star's blinding light[reference:92]. It's a bit like putting your thumb over a flashlight while searching a dark room for a firefly[reference:93]. Though the bulb vanishes, stray glare can still escape and overwhelm the light of the insect[reference:94].
Roman's coronagraph attempts something completely unseen in space telescopes until this year: before each observation, it measures that leftover light and tries to suppress it — a technique known as active wavefront control[reference:95].
The telescope achieves this with two deformable mirrors, each featuring a 48-by-48 checkerboard of actuators beneath a thin, deformable sheet of glass[reference:96]. Applying small amounts of voltage makes the actuators contract and tug their patches of mirror slightly backward, like thousands of microscopic fingers delicately sculpting a surface[reference:97].
The Science Payoff
Roman will carry a roughly 300-megapixel wide-field camera that will capture images about 100 times larger than Hubble's widest exposures at similar resolution[reference:98]. These capabilities will help astronomers unpack the mysteries of dark matter and dark energy — and detect around 100,000 new exoplanets[reference:99].
Javier Viaña, a research scientist at Harvard who has had two projects selected for Roman's highly competitive first year of observing, compares the leap to moving from "interviewing a handful of people" to "conducting a global census[reference:100]."
Another camera will use the coronagraph, blocking out a star's light as it observes one stellar system at a time[reference:101]. The instrument will allow astronomers an unprecedented look at the space around stars, enabling them to see smaller, dimmer, and more close-in exoplanets[reference:102].
"It's giving us the ability to see planets that we haven't been able to physically see before," says Creager[reference:103].
Mission Details
The Nancy Grace Roman Space Telescope is named after NASA's first chief of astronomy[reference:104]. The mission is scheduled to launch from Kennedy Space Center on August 30, 2026, with a five-year primary mission and a 10-year goal[reference:105]. It will orbit at Sun-Earth L2[reference:106].
A Stepping Stone
Roman's active coronagraph represents a critical step toward directly imaging Earth-like planets around other stars. If it succeeds, it will open a new window into planetary systems beyond our own — and bring us closer to answering one of humanity's oldest questions: are we alone?