Sept. 8, 2008 -- Scientists are using new laser technology to improve the precision of telescopes, bringing the dream of watching the expansion of the universe in real time within reach.
Published in the latest edition of Science, the researchers, including Swinburne University astronomer Michael Murphy, show how a laser frequency comb can be used to calibrate an infra-red telescope.
This will allow astronomers to more precisely measure features of distant galaxies and stars.
The comb was developed by co-author Theodor Hansch, of the Max-Planck Institute for Quantum Optics who is a joint winner of the 2005 Nobel Prize for Physics for the technology.
The comb emits pulses of light several femtoseconds in duration (a quadrillionth of a second) across a range of regularly spaced wavelengths.
"It just so happens when you link your laser frequency comb up to an atomic clock you know what those spacings are to an extremely high level of precision," said Murphy, who is based at the Center for Astrophysics and Supercomputing.
When the technology is applied to the telescope, he explained, it gives "you a ruler that measures wavelengths and you can measure how quickly things are moving."
Murphy, who is one of the chief instigators of the research, says the team succeeded in calibrating the German Vacuum Tower Telescope, an infrared telescope used to track the movement of clouds of gas on the sun.
He says it is currently difficult to calibrate telescopes in the infrared spectrum below 10 meters per second. However by using the new technique, the team managed to achieve nine meters per second calibration.
"We've taken the precision of the atomic clock and used it in astronomy for the first time," Murphy said. "Hopefully it will open up new areas in astronomy, enabling experiments that people have only dreamed of before."
The technology could reveal variations in the "fundamental constants of nature" by allowing astronomers to detect changes in the spectral signatures of clouds of gas in distant universes.
With improvements, Murphy believes the technology will also be able to calibrate spectrographs to record changes in velocity to an accuracy of one centimeter per second in the opitcal range.
Murphy is part of a project slated for the European Southern Observatory's planned 42-meter diameter European Extremely Large Telescope that hopes to measure the expansion of the universe by tracking redshift drift over a 20-year period.
Light from an object moving away from an observer will be stretched towards the red end of the spectrum, in an effect known as "redshift."
University of Queensland astrophysicist Tamara Davis says the research has generated excitement about future research possibilities.
Davis says the improved precision of calibration for the telescopes will allow astronomers to be certain that measurements made at different times are comparable.
"The kinds of measurement we want to make are looking at the expansion of the universe and how that changes with time," Davis said.
"But things on the scale of the universe don't change much over a human lifespan."
She says at present the expansion of the universe can only be tracked in "snapshots" with measurements taken at different times.
This technology will provide a "movie" of a galaxy's evolution through time.
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