Star Shades

One problem with finding planets, especially habitable ones, is that they are near stars, which give off far more light than the planets themselves reflect. Typical telescopes utilize a coronagraph, or light shield, to filter out this extraneous light. A new story in Nature, by Webster Cash of the University of Colorado in Boulder, suggests an alternative. He proposed moving the light shield outside the telescope, in a petal shape approximately 35 meters wide and placed 20,000 kilometers from the telescope. According to principles developed by Augstin Fresnel in the 19th century, Cash believes that such a shield would block extraneous light while still negating diffraction in the observed images, allowing astronomers to more readily detect planets that would have earthlike conditions.

For More Information:

• Nature: "Starshade could make planet-hunting cheap"
• Science: "A Stellar Pair of Shades"
• Scientific American: "Star Shade Could Reveal Earthlike Exoplanets"