Roman Coronagraph Digging the Dark Hole

The Roman Coronagraph Instrument on NASA's upcoming Nancy Grace Roman Space Telescope will test new tools that block starlight, revealing planets hidden by the glare of their parent stars. This graphic shows a test of what engineers call "digging the dark hole." The image shows three computer readouts of real data from the coronagraph's camera. Engineers used lasers and special optics to replicate the light from a star as it would look when observed by the Roman telescope. The image at left shows the amount of starlight that leaks into the coronagraph's field of view when only fixed components called masks are used to block the star at the center of the circle. Using moveable components such as deformable mirrors, the coronagraph can remove more and more of this starlight. The middle and right images show the progression of this process, where red indicates less starlight, and black indicates most or all starlight has been removed. The deformable mirrors are each only 2 inches (5 centimeters) in diameter and backed by more than 2,000 tiny pistons that move up and down. The pistons work together to change the shape of the mirrors to compensate for the unwanted stray light that spills around the edges of the masks. Though they are too small to affect Roman's other highly precise measurements, the imperfections can send stray starlight into the dark hole. In space, this technique will enable astronomers to observe light directly from planets around other stars, or exoplanets. Once demonstrated on Roman, similar technologies on a future mission could enable astronomers to use that light to identify chemicals in an exoplanet's atmosphere, potentially indicating the presence of life. https://photojournal.jpl.nasa.gov/catalog/PIA26279