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A. Quirrenbach (Leiden Observatory)
An Extremely Large Synthesis Array (ELSA) with 27 ten-meter telescopes and baseline lengths up to 10km would provide new insight into many astrophysical phenomena that are completely inaccessible to any other instrument. For example, it could be used to obtain resolved images of nearby brown dwarfs which would reveal weather phenomena in their atmospheres, to give detailed pictures of stellar surfaces, interacting binaries, and circumstellar material, to study general-relativistic effects on the orbits of stars near the center of our Galaxy, to obtain "movies" of expanding supernovae, to image the broad-line regions of active galaxies, and to measure the geometry of the fireballs producing the afterglows of gamma-ray bursts.
Observations of faint objects will be possible by using an external reference star (within the isoplanatic angle) to co-phase the array. Large telescopes equipped with laser guide star adaptive optics can provide good sky coverage in this observing mode. The use of optical fibers for beam transport and delay compensation would be highly beneficial, as this would eliminate the need for an expensive beam train with meter-sized optical elements, and a very large vacuum system. The most challenging aspect of fiber-coupled interferometry is dispersion in the fibers, which has to be eliminated or compensated precisely.
Advances in telescope technology and fiber optics expected for the next decade may bring the cost of a facility similar to the ELSA concept discussed here into a range that would be affordable as an international project.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.