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April 18, 2010

Direct Imaging of Exoplanets Using Optical Vortex Coronagraphs Using Telescopes With Five Times Smaller Diameter

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Universe Today - exoplanets orbit the star HR 8799, and have been imaged directly before, by one of the 10-meter (33-foot) Keck telescopes and the 8.0-meter (26-foot) Gemini North Observatory in 2008 Now they have been imaged by using just a 1.5-meter-diameter (4.9-foot) portion of the famous Palomar 200-inch (5.1 meter) Hale telescope's mirror. They did it by working in the near infrared, and by combining two techniques – adaptive optics and a coronagraph.

The Vector Vortex Coronagraph: Laboratory Results and First Light at Palomar Observatory

High-contrast coronagraphy will be needed to image and characterize faint extra-solar planetary systems. Coronagraphy is a rapidly evolving field, and many enhanced alternatives to the classical Lyot coronagraph have been proposed in the past ten years. Here, we discuss the operation of the vector vortex coronagraph, which is one of the most efficient possible coronagraphs. We first present recent laboratory results, and then first light observations at the Palomar observatory. Our near-infrared H-band (centered at ~ 1.65 microns) and K-band (centered at ~ 2.2 microns) vector vortex devices demonstrated excellent contrast results in the lab, down to ~ 1e-6 at an angular separation of 3 lb/d. On sky, we detected a brown dwarf companion 3000 times fainter than its host star (HR 7672) in the Ks band (centered at ~2.15 microns), at an angular separation of ~ 2.5 lb/d. Current and next-generation high-contrast instruments can directly benefit from the demonstrated capabilities of such a vector vortex: simplicity, small inner working angle, high optical throughput (>90%), and maximal off-axis discovery space.


Further development of improved visible devices is ultimately aimed at providing a close to ideal coronagraph for exoplanet space missions such as the Actively Corrected Coronagraph for Exoplanet Space Studies, paving the way towards the Terrestrial Planet Finder Coronagraph. (6 page pdf)



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