August 2009 — A laser comb for astronomy

Artist’s impression of a laser comb developed for astronomy. Such a device is necessary to calibrate the new, extremely precise spectrographs that will search for Earth-like planets and measure the expansion of the Universe. The new calibration technique is a combination of astronomy and quantum optics, the result of a collaboration between researchers at ESO and the Max-Planck-Institute for Quantum Optics. It uses ultra-short pulses of laser light to create a “frequency comb” — light at many frequencies separated by a constant interval — forming just the kind of precise “ruler” needed to calibrate a spectrograph to about one part in 30 billion. A feat equivalent to measuring the circumference of the Earth to about a millimetre!

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