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Middle English, from Anglo-French arraier, from Vulgar Latin arredare, from Latin ad- + a base of Germanic origin; akin to Gothic garaiths arranged


  • 1: to dress or decorate especially in splendid or impressive attire : adorn <he had already arrayed himself in his best clothes — Thomas Hardy>
  • 2a : to set or place in order : draw up, marshal <the forces arrayed against us>
b : to set or set forth in order (as a jury) for the trial of a cause
  • 3: to arrange or display in or as if in an array <the … data are arrayed in descending order — Ed Burnett>


An astronomical interferometer is an array of telescopes or mirror segments acting together to probe structures with higher resolution by means of interferometry. The benefit of the interferometer is that the angular resolution of the instrument is nearly that of a telescope with the same aperture as a single large instrument encompassing all of the individual photon-collecting sub-components. The drawback is that it does not collect as many photons as a large instrument of that size. Thus it is mainly useful for fine resolution of the more luminous astronomical objects, such as close binary stars.

Astronomical interferometers are widely used for optical astronomy, infrared astronomy, submillimetre astronomy and radio astronomy. Aperture synthesis can be used to perform high-resolution imaging using astronomical interferometers. Very Long Baseline Interferometry uses a technique related to the closure phase to combine telescopes separated by thousands of kilometers to form a radio interferometer with the resolution which would be given by a single dish which was thousands of kilometers in diameter. At optical wavelengths, aperture synthesis allows the atmospheric seeing resolution limit to be overcome, allowing the angular resolution to reach the diffraction limit of the array.

Astronomical interferometers can produce higher-resolution astronomical images than any other type of telescope. At radio wavelengths image resolutions of a few micro-arcseconds have been obtained, and image resolutions of a fractional milliarcsecond have been achieved at visible and infrared wavelengths.

One simple layout of an astronomical interferometer is a parabolic arrangement of mirrors, giving a partially complete reflecting telescope (with a "sparse" or "dilute" aperture). In fact the parabolic arrangement of the mirrors is not important, as long as the optical path lengths from the astronomical object to the beam combiner or focus are the same as given by the parabolic case. Most existing arrays use a planar geometry instead, and Labeyrie's hypertelescope will use a spherical geometry, for example[1]