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| Version | Summary | Created by | Modification | Content Size | Created at | Operation |
|---|---|---|---|---|---|---|
| 1 | Camila Xu | -- | 1919 | 2022-10-12 01:37:37 |
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An astronomical interferometer is an array of separate telescopes, mirror segments, or radio telescope antennas that work together as a single telescope to provide higher resolution images of astronomical objects such as stars, nebulas and galaxies by means of interferometry. The advantage of this technique is that it can theoretically produce images with the angular resolution of a huge telescope with an aperture equal to the separation between the component telescopes. The main drawback is that it does not collect as much light as the complete instrument's mirror. Thus it is mainly useful for fine resolution of more luminous astronomical objects, such as close binary stars. Another drawback is that the maximum angular size of a detectable emission source is limited by the minimum gap between detectors in the collector array. Interferometry is most widely used in radio astronomy, in which signals from separate radio telescopes are combined. A mathematical signal processing technique called aperture synthesis is used to combine the separate signals to create high-resolution images. In Very Long Baseline Interferometry (VLBI) radio telescopes separated by thousands of kilometers are combined to form a radio interferometer with a resolution which would be given by a hypothetical single dish with an aperture thousands of kilometers in diameter. At the shorter wavelengths used in infrared astronomy and optical astronomy it is more difficult to combine the light from separate telescopes, because the light must be kept coherent within a fraction of a wavelength over long optical paths, requiring very precise optics. Practical infrared and optical astronomical interferometers have only recently been developed, and are at the cutting edge of astronomical research. 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 optics. 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 mirror pieces, giving a partially complete reflecting telescope but 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 (focus) are the same as would be given by the complete mirror case. Instead, most existing arrays use a planar geometry, and Labeyrie's hypertelescope will use a spherical geometry.
References
- Michelson, Albert Abraham; Pease, Francis G. (1921). "Measurement of the diameter of alpha Orionis with the interferometer". Astrophysical Journal 53: 249–59. doi:10.1086/142603. Bibcode: 1921ApJ....53..249M.
- Johnson, M. A.; Betz, A. L.; Townes, C. H. (December 30, 1974). "10-micron heterodyne stellar interferometer". Physical Review Letters 33 (27): 1617–1620. doi:10.1103/PhysRevLett.33.1617. Bibcode: 1974PhRvL..33.1617J.
- "Interference fringes obtained on VEGA with two optical telescopes". Astrophysical Journal 196 (2): L71–L75. March 1, 1975. doi:10.1086/181747. Bibcode: 1975ApJ...196L..71L.
- Baldwin, John E.; Haniff, Christopher A. (May 2002). "The application of interferometry to optical astronomical imaging,". Royal Society of London 360 (1794): 969–986. doi:10.1098/rsta.2001.0977. Bibcode: 2002RSPTA.360..969B. Retrieved 2010-09-27. "A postscript version of the article can also be downloaded at: Coast papers".
- Baldwin, J. E.; Beckett, M. G.; Boysen, R. C.; Burns, D.; Buscher, D. F. et al. (February 1996). "The first images from an optical aperture synthesis array: mapping of Capella with COAST at two epochs". Astronomy and Astrophysics 306: L13. Bibcode: 1996A&A...306L..13B.
- Baldwin, John E. (February 2003). "Ground-based interferometry: the past decade and the one to come". Proceedings of the SPIE. Interferometry for Optical Astronomy II 4838: 1–8. doi:10.1117/12.457192. Bibcode: 2003SPIE.4838....1B. Retrieved 2010-09-27. "This paper aims to give a broad view of the progress achieved in ground-based interferometry over the past ten years and to assess quantitatively the factors determining the types of object that can be observed with high resolution over the next ten. A postscript version of the article can also be downloaded at: PostScript file download".
- Benson, J. A.; Hutter, D. J.; Elias, N. M., II; Bowers, P. F.; Johnston, K. J.; Hajian, A. R.; Armstrong, J. T.; Mozurkewich, D.; Pauls, T. A.; Rickard, L. J.; Hummel, C. A.; White, N. M.; Black, D.; Denison, C. S. (1997). "Multichannel optical aperture synthesis imaging of zeta1 URSAE majoris with the Navy prototype optical interferometer.". The Astronomical Journal 114: 1221. doi:10.1086/118554. Bibcode: 1997AJ....114.1221B.
- Hummel, C. A.; Benson, J. A.; Hutter, D. J.; Johnston, K. J.; Mozurkewich, D.; Armstrong, J. T.; Hindsley, R. B.; Gilbreath, G. C.; Rickard, L. J.; White, N. M. (2003). "First Observations with a Co-phased Six-Station Optical Long-Baseline Array: Application to the Triple Star eta Virginis". The Astronomical Journal 125: 2630. doi:10.1086/374572. Bibcode: 2003AJ....125.2630H.
- "New Hardware to Take Interferometry to the Next Level". ESO. Retrieved 3 April 2013.
