NASA’s Roman Space Telescope just took its first test image with its coronagraph. The instrument will one day photograph planets around other stars. How does a coronagraph work?

A coronagraph blocks the blinding light of a star. Planets are billions of times fainter than their stars. Without blocking the starlight, the planet’s faint glow is lost in the glare.

Roman’s coronagraph uses masks and deformable mirrors. The mirrors change shape thousands of times per second. They cancel out tiny distortions in the starlight. This creates a dark zone where a faint planet can appear.

The September 22 test did not block any starlight yet. It only proved the instrument can take a focused image. A second sharper test followed on September 27. Once working fully, the coronagraph will demonstrate technology for future missions. NASA’s planned Habitable Worlds Observatory will use it to search for Earth-like planets. The technology could one day help find signs of life in the atmospheres of distant worlds.