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A Starshade Overview

Want to build a starshade to spot Earth-like worlds around other stars? Start with a Hubble-like telescope a few million miles from Earth. Add a 30-meter wide disk with petal-like extensions, separated by 10,000 miles from the telescope. Watch what happens next.

Using lasers, the two parts would line up, with the star shade just blocking out the light from a nearby star from the center of the telescope’s view. Calculated mathematically to throw away the light from the star but keep the light from any planets it held (this is the “occulting” part of the occulted), the device would be able to detect planets smaller than Earth orbiting stars within 35 light years of Earth, Cash and his colleagues calculate. The key is the petal shape of the shade, which scatters starlight from the telescope’s view.

From an overview of planet-finder technologies by Dan Vergano in USA Today. Webster Cash, whose name is frequently found in the Centauri Dreams archives, is a major part of the story.

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  • Adam February 7, 2007, 2:42

    Hi Paul

    Not a bad article. What could improve the practicality of planet hunting is smart-material primary mirrors that can fold up for launch and unfold to a high level of optical precision. Then we could launch huge primary mirrors for in-space telescopes, incrementally adding telescopes to a vast interferometer/coronagraph/occluder network of space scopes.

    There are materials that could do the job – the military has a vested interest in big mirrors pointing down to the Earth and is researching such systems assiduously.


  • ljk February 7, 2007, 9:15

    In 1979, the Soviets conceived of an “Infinitely Built-Up Space
    Radio Telescope”:


    And a more recent proposal to use lots of small satellites
    as shades to cool Earth could be turned into mirrors for
    making a giant space telescope:


  • Adam February 8, 2007, 1:15

    Hi Larry

    Of course! The old telescope in the Sunshade trick! Ingenious!

    Adam :-)