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‘Laser Comb’ May Aid Search for Earth-Like Alien Planets

Image: This picture illustrates part of a spectrum of a star obtained using the HARPS instrument on the ESO 3.6-metre telescope at the La Silla Observatory in Chile. Credit: ESO

Astronomers searching for alien planets may be a step closer to finding true Earth-like worlds around sun-like stars, by using a new tool that promises to increase the accuracy of planet-hunting instruments tenfold, scientists say.

The laser frequency comb is a calibration tool specifically designed for large ground-based telescopes that search for alien planets through the “wobble method,” which identifies extrasolar planets by the gravitational effect (the wobble) they have on their parent stars.

Today instruments such as the European Southern Observatory’s High Accuracy Radial Velocity Planet Searcher (HARPS) spectrograph on a telescope in Chile observe planets via the wobble method. But precision is key, and the hollow cathode lamps used to calibrate those spectrometers have their limitations, researchers said — 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.

“To detect low-mass planets — down to the Earth mass — in Earth-like orbits requires a precision 10 times better,” study co-author Gaspare Lo Curto of the European Southern Observatory said.

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