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Proceedings Paper

First results of nulling interferometry with the Multiple-Mirror Telescope
Author(s): Philip M. Hinz; James Roger P. Angel; William F. Hoffmann; Donald W. McCarthy Jr.; Patrick C. McGuire; Matthew Cheselka; Joseph L. Hora; Neville J. Woolf
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Paper Abstract

We have successfully used nulling interferometry at 10 μm wavelength to interferometrically suppress a star's radiation. This technique was first proposed by Bracewell 20 years ago to image extra-solar planets and is now the basis for proposed space-borne instruments to search for Earth-like extra-solar planets and their spectroscopic signatures of habitability and life. In our experiment, the beams from two 1.8 m telescopes of the Multiple Mirror Telescope were brought into registration at a semi-transparent beamsplitter, and the images made coincident on an infrared array detector capable of taking rapid short exposure images. The atmospheric fluctuations caused the phase difference between the beams to fluctuate, changing the total flux of the star seen in the image plane. When the atmosphere caused the wavefronts to be exactly out of phase the entire stellar Airy pattern disappeared. For the unresolved star α Tauri the cancellation was such that a companion only 0.2 arcsec from the star and 25 times fainter would appear equal in intensity to the nulled star. The residual flux was spread into a wide halo suggesting the cause of this flux was imperfect cancellation of the aberrated wavefronts. To increase the precision of nulling beyond this first step several sources of error need to be addressed. We discuss the control of errors due to amplitude, polarization, chromatic differences, stellar leak, and sampling time. Improvements such as active phase tracking, adaptive optics, and cooled optics will increase the achievable gain of nulling interferometry and allow it to be used on fainter objects.

Paper Details

Date Published: 24 July 1998
PDF: 9 pages
Proc. SPIE 3350, Astronomical Interferometry, (24 July 1998); doi: 10.1117/12.317108
Show Author Affiliations
Philip M. Hinz, Steward Observatory/Univ. of Arizona (United States)
James Roger P. Angel, Steward Observatory/Univ. of Arizona (United States)
William F. Hoffmann, Steward Observatory/Univ. of Arizona (United States)
Donald W. McCarthy Jr., Steward Observatory/Univ. of Arizona (United States)
Patrick C. McGuire, Steward Observatory/Univ. of Arizona (United States)
Matthew Cheselka, Steward Observatory/Univ. of Arizona (United States)
Joseph L. Hora, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Neville J. Woolf, Steward Observatory/Univ. of Arizona (United States)

Published in SPIE Proceedings Vol. 3350:
Astronomical Interferometry
Robert D. Reasenberg, Editor(s)

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