NASA's Giant Sunglasses Could Allow Space Telescopes to Take Pictures of Habitable Worlds

"If and only if it has a starshade, WFIRST could give us images of a few true-blue Earths late next decade rather than waiting for another 20 years," Jeremy Kasdin, a Princeton University professor and lead scientist for WFIRST's coronagraph, told Scientific American . "This is a real opportunity to find another Earth sooner and for less money before making a huge investment in NASA's next giant space telescope."

"We call this being 'starshade ready,'" Kasdin said. "This is not in WFIRST's current design, and we can't just put these changes off indefinitely…. By next year we pretty much need to have decided whether we're going to make it starshade-ready or not."

NASA is about to launch the groundbreaking James Webb Space Telescope in 2018, but even with that state-of-the-art technology, we still won't be able to image potentially habitable worlds in other star systems. Now, that might be about to change, as NASA is working on an engineering project called "Starshade," which would essentially serve as sunglasses for space telescopes and allow us to take pictures of promising exoplanets.In addition to James Webb, NASA is currently working on the Wide-Field Infrared Survey Telescope (WFIRST), an even bigger observatory that is planned to launch in 2025. The telescope would be equipped with a mirror the same size as Hubble's—2.4 meters—but would be able to take views of the universe with its Wide Field Instrument camera that are a hundred times larger than our current space telescope. These powerful panoramic views will allow the WFIRST to study dark matter, but also may be able to show us views of Earth-like planets for the first time.It's extremely difficult to take images of exoplanets; for Earth-bound telescopes, out thick atmosphere blocks any possible views, but neither Hubble nor James Webb have the contrast needed to view objects in other solar systems. WFIRST will mitigate this problem with a coronograph, which will filter out starlight using masks, mirrors and lenses. But since the coronograph was created late in the game, the telescope's mirror isn't optimized for it, so it will probably only allow WFIRST to view larger planets, such as gas giants and, at best, "mini-Neptunes," which are approximately twice the size of Earth and most likely don't host recognizable life.But there may be one other supplemental technology that will still allow the WFIRST to image Earth-like exoplanets: the Starshade. This sunflower-shaped screen is as thin as paper, and unfolds somewhat like a pinwheel. It's only half as large as a football field, but can block the light from a star by hovering thousands of kilometers in front of the telescope, similar to blocking out the sun's light with one's hand.Currently, NASA JPL researchers are demonstrating exactly how the starshade would work, were it added to the WFIRST. It would potentially be able to fold to a very small size, fit inside of a rocket, and then deployed and unfurled in space once the WFIRST is ready to start taking pictures. However, the decision to include the starshade needs to happen very soon, since certain modifications would need to be made to the WFIRST's technology in order to allow them to work in tandem with each other.