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STARSHADE concept could enable direct exoplanets detection as early as the 2020’s.
STARSHADE
Made in the Shade—Finding Life in the Shade of a Star
Daniel Wilson
Up to half the size of a football field, a starshade would journey into space as a companion to a telescope, deploy and unfurl its “petals”, and fly in formation up to 50,000 kilometers away from the telescope to take position in front of a star of interest. The unique shape of the flower-like starshade creates a near-perfect shadow of the star, allowing the telescope to reveal the planets orbiting in its habitable zone—the Goldilocks “not too hot and not too cold” distance from the star.
The universe is teeming with planets. Astronomers now believe that every star in the galaxy has a planet, and they speculate that up to one fifth of them has an Earth-like planet in the right orbit that might be able to harbor life, but we haven’t seen any of them. We’ve only detected them indirectly because they are too dim and too close to their parent stars — all we’re currently seeing is the big beaming image of the star that’s ten billion times brighter than the planet. The light from the star creates a very bright image inside the telescope that washes out the tiny planet.
It’s kind of like being on stage and putting your hand in front of the spotlight shining in your eyes to see someone in the back row. But imagine you are in Los Angeles trying to see a baseball that’s close to a large searchlight pointing right at you… from San Francisco. It’s the same to see the planet; not only do we need to see something very tiny, we have to get rid of all that starlight.
In summer 2015, the team tested a half scale model of a 34m diameter deployable starshade structure at JPL. To be successful, 7m long petals need to unfurl with a shape that is precise to within a few human hair widths. The structure must then rotate, deploy and position the petals around a 20m diameter central disc structure to within a fraction of a millimeter. The petal shapes and positions must then stay that way for years in the harsh space environment. The team showed with 20 deployments that the structure places the petals to within about a tenth of a millimeter of the correct spot every time. These successful tests take us another step closer to getting a picture, a star’s family portrait of planets made in the shade, where we may just see another pale blue dot that could harbor life.
