The coronagraph on NASA’s Nancy Grace Space Telescope will help pave the way for the search for planets outside our solar system. The technology demonstration recently launched from NASA’s Jet Propulsion Laboratory (JPL) in Southern California, where it joins the rest of the space observatory in preparation for launch in May 2027.

Before the flight, the coronagraph underwent a full test of its ability to block starlight; process engineers call this “cutting through a dark hole.” This process will allow astronomers to directly observe light from planets around other stars. When similar technologies are demonstrated on a future mission, it could allow astronomers to use the data to identify chemicals in exoplanet atmospheres, including those that potentially indicate biomarkers.

During testing, the coronagraph camera shows a ring-shaped region around the observed star that gradually darkens as the team directs more starlight away from it; hence the name of the process “dark hole etching”. An exoplanet lurking in this dark region will gradually emerge as the device continues its work with moving, deforming mirrors.

More than 5,000 planets have been discovered and confirmed around other stars in the last 30 years, but most of these were discovered indirectly; This means that their existence is determined by how they appear in the light of their star. In fact, fewer than 70 exoplanets have been imaged directly, and they tend to be much larger, hotter, and farther from their stars than Earth.

Developing direct imaging capabilities for terrestrial planets will require intermediate steps such as the coronagraph on the Nancy Grace Roman telescope. At maximum power, it can image a Jupiter-like exoplanet around a star like our Sun: a large, cold planet just outside the star belt.

What NASA engineers learn from this coronagraph will help pave the way for future missions designed to directly image Earth-sized planets orbiting in regions of Sun-like stars. The future telescope concept, called the Habitable Worlds Observatory, aims to image at least 25 Earth-like planets with an instrument that would build on the achievements of the Nancy Grace coronagraph.

“Active components like deformable zeforms are necessary to achieve the goals of a mission like the Inhabited Worlds Observatory. The active nature of the Roman coronagraph allows you to elevate normal optics to a new level. This complicates the entire system, but without it we wouldn’t be able to do all these incredible things,” he said. Ilya Poberezhskiy of the Jet Propulsion Laboratory, systems engineer for the coronagraph project.