Science Focus
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Late in May, at a session of the World Science Festival devoted to the prospects of finding life on other planets, astronomer Sara Seager came with a rather unusual looking stage prop—a thin black slab that tapered at one end. It sat off on the side of the stage for a while before Seager got the chance to explain what it was doing there. When she finally got the chance, she said why it could be the key to imaging small, rocky planets like Earth—and determining if their atmospheres provide hints that there might be life on the surface below.
So far, the only planets outside our solar system that we've imaged directly have been huge gas giants, far from their host star and young enough to still be glowing in the infrared. Even with their relative brightness and distance from the nearest star, the light from the star would completely swamp our sensors. So the telescopes used to contain what's called a coronagraph, or star shade. This blots out the central star, ensuring that the majority of light the telescope receives comes from the planets.
But small planets close enough to be in the habitable zone of a star create two problems. The first is that they don't produce any of their own light; instead, we'd have to capture light that's produced by the host star and then reflected off their surfaces or atmospheres. This makes them very dim, especially relative to their host star.
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