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19 August 2009A starshade for JWST: science goals and optimization
The James Webb Space Telescope will be an extraordinary observatory, providing a huge range of exciting new
astrophysical results. However, by itself it will not be capable of directly imaging planets in the habitable zone of
nearby stars, one of the most fascinating goals of astronomy for the coming decade. In this paper we discuss the
New Worlds Probe (NWP) concept whereby we use an external occulter (or starshade) to cast a shadow from
the star onto the telescope, therefore canceling the direct star light while the light from a planet is not affected.
This concept enables JWST to take images and spectra of extrasolar planets with sufficient contrast and inner
working angle to be able to discover planets down to the size of the Earth in the habitable zone around nearby
stars. JWST's instruments are appropriate to achieve low resolution spectroscopy (R ≅ 40) of these planets, and
address a series of fundamental questions: are there planets in the habitable zone around nearby stars? What
is the composition of their atmosphere? What are the brightness and structures of exozodiacal disks around
nearby stars? What is the mass and composition of currently known giant planets? In this paper we study the
starshade optimization for JWST given the instrumental constraints, and show that the modest optical quality
of the telescope at short wavelength does not impact the possibility of using a starshade. We propose a solution
to enable imaging and spectroscopy using target acquisition filters. We discuss possible time allocation among
science goals based on exposure time estimates and total available observing time. The starshade can be launched
up to 3 years after JWST and rendezvous with the telescope in orbit around L2.
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Rémi Soummer, Webster Cash, Robert A. Brown, Ian Jordan, Aki Roberge, Tiffany Glassman, Amy Lo, Sara Seager, Laurent Pueyo, "A starshade for JWST: science goals and optimization," Proc. SPIE 7440, Techniques and Instrumentation for Detection of Exoplanets IV, 74400A (19 August 2009);