Detection of Earth-like Planets Using Apodized Telescopes

The mission of NASA's Terrestrial Planet Finder (TPF) is to find Earth-likeplanets orbiting other stars and characterize the atmospheres of these planetsusing spectroscopy. Because of the enormous brightness ratio between the starand the reflected light from the planet, techniques must be found to reduce thebrightness of the star. The current favorite approach to doing this is withinterferometry: interfering the light from two or more separated telescopeswith a $\pi$ phase shift, nulling out the starlight. While this technique can,in principle, achieve the required dynamic range, building a spaceinterferometer that has the necessary characteristics poses immense technicaldifficulties. In this paper, we suggest a much simpler approach to achievingthe required dynamic range. By simply adjusting the transmissive shape of atelescope aperture, the intensity in large regions around the stellar image canbe reduced nearly to zero. This approach could lead to construction of a TPFusing conventional technologies, requiring space optics on a much smaller scalethan the current TPF approach.Comment: Accepted for publication in ApJ Letters, 9 pages, 6 figure