The proposed spacecraft was designed to work in tandem with space telescopes like the James Webb Space Telescope, which did not use it, or a new 4-meter telescope. The starshade is a spacecraft designed by Webster Cash, an astrophysicist at the University of Colorado at Boulder's Center for Astrophysics and Space Astronomy. The "petals" of the "sunflower" shape of the starshade are designed to eliminate the diffraction that is the central feature of an Aragoscope. The starshade is a proposed sunflower-shaped coronagraph disc that was designed to block starlight that interferes with telescopic observations of other worlds.
The starshade is similar to but should not be confused with the Aragoscope, which is a proposed imaging device designed to use the diffraction of light around a perfectly-circular light-shield to produce an image. It is estimated that there could be as many as several thousands of exoplanets within that distance. This technique would make planetary detection possible for stars within approximately 10 parsecs (about 32 light years) of Earth. By adding specially shaped petals to the outer edge of the disc, the spot of Arago will disappear, allowing the suppression of the star's light. This effect can be negated by specifically shaping the occulter. However Dominique Arago experimentally verified the existence of the spot of Arago. This concept was first famously theorized by Siméon Poisson in order to disprove the wave theory of light, as he thought the existence of a bright spot at the center of the shadow to be nonsensical. Thus the starlight would still be easily visible, making planet detection impossible. One difficulty with this concept is that light incoming from the target star would diffract around the disc and constructively interfere along the central axis. The disc would likely be several tens of meters in diameter and would fit inside existing expendable launch vehicles and be deployed after launch. The occulter would be a large sheet disc flown thousands of kilometers along the line of sight. This would allow the direct observation of orbiting planets. The goal of the New Worlds Mission is to block the light coming from nearby stars with an occulter. The blue circle represents the planet, whose light passes to the observer undisturbed. The yellow circle represents the star, whose light is blocked by the occulter. The starshade would be tens of meters across and probably made out of Kapton, a lightweight material similar to Mylar.
The occulter would block all of the starlight from reaching the observer, while allowing the planet's light to pass undisturbed. To overcome the difficulty of distinguishing more Earth-like planets in the vicinity of a bright star, the New Worlds Mission would block the star's light with an occulter. Furthermore, the planet is orbiting a very dim star, known as a brown dwarf.
Astronomers were only able to photograph this planet because it is a very unusual planet that is very far from its host star, approximately 55 astronomical units (about twice the distance of Neptune).
The first exoplanet to be photographed, 2M1207b, is in orbit around a star called 2M1207. To date, only a handful of exoplanets have been photographed. The difficulty of observing such a dim planet so close to a bright star is the obstacle that has prevented astronomers from directly photographing exoplanets. This makes it nearly impossible to see planets against the star's glare. Typically, the star will be approximately a billion times brighter than the orbiting planet.
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