Laser frequency combs aid the search for exoplanets

Laser Focus World ^ | Saturday, June 2, 2012 | John Wallace

[SunkenCiv]

A team of scientists headed by Theodor Hänsch from the Laser Spectroscopy Division at the Max Planck Institute of Quantum Optics has collaborated with researchers from the European Southern Observatory (ESO), the Instituto de Astrofísica de Canarias, and Menlo Systems GmbH (Martinsried) in modifying the optical frequency-comb technique in a way that it can be applied for the calibration of astronomical spectrographs. Hänsch is one of the inventors of the optical frequency comb.

The new instrument has been tested successfully with the High Accuracy Radial velocity Planet Searcher (HARPS), a spectrograph at the 3.6 m telescope at the La Silla Observatory in Chile. A tenfold improvement of precision was obtained as compared with traditional spectral lamp calibrators. This should greatly enhance the chances to find earthlike planets outside our solar system.

These planets cannot be imaged directly, even with the largest telescopes. One of the most successful detection methods is the measurement of the small Doppler shifts in the spectrum of the parent star due to the recoiling motion caused by the planet. The star's light contains numerous spectral lines characteristic of the different chemical elements in the star's gas atmosphere. When the star is moving towards or away from the observer, these lines are shifted to slightly higher or lower frequencies; this shift is what is measured to determine the presence of an exoplanet...

[SunkenCiv]

The frequency difference (fr) between two neighboring lines in a frequency comb is always exactly the same. It is kept stable by comparing it with an atomic clock. The comb light is guided to the spectrograph in an optical fiber. The light is separated into its its frequency components by the spectrograph and imaged on the CCD detector. The comblike spectrum appears as a row of dots, of which each dot corresponds exactly to one line of the frequency comb. This "laser ruler" can now be used to calibrate the spectrograph. (Image: T. Wilken)

[SunkenCiv]

Frequency combs to join the hunt for exoplanets
May 31, 2012
http://physicsworld.com/cws/article/news/2012/may/31/frequency-combs-to-join-the-hunt-for-exoplanets

[SunkenCiv]

· join · view topics · view or post blog · bookmark · post new topic · subscribe ·

Google news searches: exoplanet · exosolar · extrasolar ·

[ClearCase_guy]

You know who really needs a laser frequency comb? This guy:

[MD Expat in PA]

Actually I think he really needs to lay off the laser frequency comb. : )

[SunkenCiv]

He watched too much Bab5.