Thursday, 31 May 2012

‘Laser comb’ could help find alien planets

A new tool could aid planet hunters in the search for Earth-like alien planets.
Scientists published a study in the May 31 edition of the journal Nature in which they detail results from testing their laser frequency comb–a calibration tool for large ground-based planet-hunting telescopes. Some of these telescopes locate planets by observing the gravitational effect, or wobble, these potential planets have on their parent stars. Current tools are reportedly limited in function, and lack precision. For example, the European Southern Observatory’s High Accuracy Radial Velocity Planet Searcher (HARPS) spectrograph on a telescope at the La Silla Observatory in Chile searches for planets using this “wobble method.” 

The La Silla Observatory in Chile. (Credit: ESO)

But according to, “precision is key, and the hollow cathode lamps used to calibrate those spectrometers have their limitations . . . they are not adjustable, can be difficult to gauge, and allow the spectrometers to track the wobble of a star only down to about 30 centimeters per second.” And, as study co-author Gaspare Lo Curto of the European Southern Observatory explains, the detection of Earth-sized planets requires that precision, multiplied by ten.

Lo Curto and his colleagues tested the laser frequency comb on the HARPS. The researchers claim this tool provides the required accuracy enhancement. explains that the laser frequency comb works by emitting “many lines of light spread apart like the teeth of a comb.” And because the distance between these “teeth” is known, it is possible to more accurately gauge “wobble.”
Although the laser comb is capable of detecting planets with masses similar to Earth, the limitations of the telescopes themselves currently prevent this. Researchers say that the HARPS, even with a laser comb, would not be capable of detecting planets less massive than Neptune-size planets in the habitable zone around sun-like stars. For reference, Neptune’s mass is seventeen times that of Earth. But optimistic researchers contend that larger telescopes currently being constructed, when fit with a laser comb, will be able to detect Earth-mass planet in the habitable zone of a sun-like star.