An accurate speedometer for astronomy

This release is available in German.

An optical fiber is used to guide the light collected in telescopes to the spectrograph, where it is split up into its individual colors. These are then compared with the... Click here for more information.

Events on a cosmic scale are often barely discernable on Earth. This explains why astronomers are currently not able to prove directly that the universe is expanding at an ever increasing rate, nor can they search for planets that are roughly the same size as Earth and revolve around a sun-like star. An international team of researchers working with staff at the Max Planck Institute of Quantum Optics has now tested a measurement method that will allow such measurements to be carried out. The scientists use a frequency comb to determine the colour of the light emitted by a celestial body with great accuracy. In a frequency comb, spectral lines, whose colour can be very accurately determined, are lined up in sequence. The physicists then compare these spectral lines with the spectrum of astronomical sources. Their aim for the future is to use this method to determine velocity changes of astronomical bodies with an accuracy of one centimetre per second. This would make their method a thousand times more precise than the methods currently available, and would enable them to search for Earth-like planets or to test whether the expansion of the universe really is accelerating. (Science, September 5, 2008)