NASA's Nancy Grace Roman Space Telescope is set to launch, featuring a primary instrument that will impact various areas of astrophysics. One notable component is a specialized coronagraph designed to capture starlight reflected off a planet's surface for the first time. This project aims to facilitate the observation of Earth-like planets orbiting sun-like stars. Vanessa Bailey, an astrophysicist at NASA's Jet Propulsion Laboratory, stated, "We’ll test them in space for the first time, and we’ll understand what work still is left to go."
A coronagraph functions as a sunshade that blocks out the light from a bright star to reveal fainter objects. While similar instruments have been used in space, Roman's coronagraph is significantly more advanced due to the incorporation of adaptive optics technology, which adjusts the telescope's mirror to counteract light distortions. Margaret Turnbull, an exoplanet scientist at the SETI Institute, noted the challenges involved, comparing the task to photographing a firefly next to a floodlight from a great distance.
Adaptive optics are standard on advanced ground-based telescopes, such as the Very Large Telescope in Chile and the Keck Observatory in Hawaii. Although space telescopes typically do not require adaptive optics, Roman will attempt to observe distant planets illuminated by reflected starlight.
The telescope's success hinges on two small mirrors equipped with approximately 2,300 actuators that reshape the mirror when electrically stimulated. This marks the first time NASA has deployed active deformable mirrors in space. The coronagraph system also relies on highly sensitive detectors to enhance signals from individual photons, which are scarce from distant planets.
Bruce Macintosh, an astronomer leading a Roman coronagraph science team, described the star shades as "beautiful, complicated shapes" that differ from the simpler designs used in previous telescopes. Engineers will collect extensive test data during the coronagraph's operations to assess its performance and identify any issues. The coronagraph will be tested against known exoplanets and will also observe stars surrounded by dust or debris to gather insights about planetary formation.
The findings from Roman's coronagraph will inform the design of future telescopes, including the Habitable Worlds Observatory, which NASA plans to launch in the 2040s, and the Lazuli Space Observatory, which will also utilize advanced coronagraph technology. Julie McEnery, an astrophysicist at NASA's Goddard Space Flight Center, emphasized the importance of demonstrating the coronagraph's capabilities through scientific discoveries.