The search for extrasolar planets has revolutionized astronomy over the last two decades, as astronomers discovered first a few, then dozens, and, now, thousands of worlds around other stars. Nearly all those planets, though, have been discovered indirectly, by watching stars periodically dim or seeing their spectral lines shift. Astronomers are now on a quest to directly observe and study exoplanets, particularly ones that could be like the Earth. That requires being able to precisely block the light from the star itself, making it possible to see the far dimmer planets that otherwise are lost in the star's glare.
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