Optical vortex coronagraph suppresses primary star of a binary system by 97%

Researchers from the University of Arizona (U of A; Tucson, AZ) and the Jet Propulsion Laboratory (Pasadena, CA) have coupled an optical vortex coronagraph (OVC) to an 8-in.

Aug 1st, 2008

Researchers from the University of Arizona (U of A; Tucson, AZ) and the Jet Propulsion Laboratory (Pasadena, CA) have coupled an optical vortex coronagraph (OVC) to an 8-in.-aperture refractive telescope at the U of A’s Steward Observatory, demonstrating the OVC’s ability to block out 97% of the light from the primary star of a resolvable binary star system without suppressing any light from the secondary star. The objective is to use the OVC in the search for spectral evidence of oxygen and water vapor in the atmospheres of extrasolar planets, perhaps eventually including an OVC on a space telescope.

In an OVC, the axis of a transparent spiral phase mask is centered on the Airy disk of the star to be blocked (in contrast to a Lyot coronagraph, which blocks the central Airy disk with an opaque disk). To compensate for star motions due to atmospheric turbulence, the researchers used a fast wavefront tip-tilt corrector in the optical system, resulting in a Strehl ratio of 99%. The OVC was tested on the Cor Caroli binary star system, which had an angular separation of 1.9 λ/D at the imaging camera. Contact Grover A. Swartzlander Jr. at grover.swartzlander@gmail.com.

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