A pair of optical telescopes have been linked for the first time by optical fibre. The technique could dramatically improve the resolution of this type of telescope, ultimately allowing us to peer into the planet-forming regions around stars.
A telescope鈥檚 resolution is dictated by its size: the greater the distance between one side of the receiver and the other, the smaller the objects it can pick out. To increase the resolution of radio telescopes without having to build ever larger receiving dishes, astronomers connect arrays of telescopes sited hundreds of metres apart or more to form interferometers. Creating large optical interferometers is harder, because light is rapidly attenuated as it travels through air. This has limited the size of optical arrays to a few hundred metres.
Optical fibres could carry light much further, and so lead to larger arrays, but until now that has been difficult to achieve, says Guy Perrin, a physicist at the Paris Observatory in France. Defects in the glass cause light pulses to spread out, making it impossible to combine the light from different telescopes in the way needed for an interferometer.
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Now Perrin and his colleagues have solved this problem. They connected the two 10-metre Keck telescopes in Hawaii using two 300-metre fluoride glass cables that were carefully matched so that they dispersed light equally along their length. When the two signals were combined the dispersion effects cancelled each other out.
Optical fibres that link telescopes across kilometres could improve resolving powers by a factor of 10, Perrin says.
