Three exoplanets around the star HR 8799 have recently been discovered by means of differential imaging with large telescopes1. Bright scattered starlight limits high-contrast imaging to large angular offsets, currently of the order of ten diffraction beamwidths, 10λ/D, of the star (where λ is the wavelength and D is the aperture diameter1,2,3,4,5). Imaging faint planets at smaller angles calls for reducing the starlight and associated photon and speckle noise before detection, while efficiently transmitting nearby planet light. To carry out initial demonstrations of reduced-angle high-contrast coronagraphy, we installed a vortex coronagraph6,7,8,9 capable of reaching small angles behind a small, well-corrected telescope subaperture that provides low levels of scattered starlight10,11. Here we report the detection of all three HR 8799 planets with the resultant small-aperture (1.5 m) system, for which only 2λ/D separate the innermost planet from the star, with a final noise level within a factor of two of that given by photon statistics. Similar well-corrected small-angle coronagraphs should thus be able to detect exoplanets located even closer to their host stars with larger ground-based telescopes12,13,14,15, and also allow a reduction in the size of potential space telescopes aimed at the imaging of very faint terrestrial planets.
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This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration, and is based on observations obtained at the Hale Telescope, Palomar Observatory, as part of a continuing collaboration between the California Institute of Technology, NASA/JPL, and Cornell University. We thank the staff of the Palomar Observatory and both the JPL and Caltech Palomar Adaptive Optics (PALAO) teams, as well as our colleagues at JDS Uniphase, where our vortex masks are manufactured.
Author Contributions All authors contributed equally to this work.
The authors declare no competing financial interests.
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Serabyn, E., Mawet, D. & Burruss, R. An image of an exoplanet separated by two diffraction beamwidths from a star. Nature 464, 1018–1020 (2010). https://doi.org/10.1038/nature09007
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