Researchers in Germany might have made the lives of exoplanet hunters so much easier, according to a paper published in the Institute of Physics (IOP) and German Physical Society's New Journal of Physics.
The team hooked up a solar telescope (Solar Vacuum Tower Telescope in Tenerife, Canary Islands) with a laser frequency comb (LFC), which will provide unprecedented accuracy of spectral analysis of distant stars, according to a press release from IOP. The technique is also expected to yield detailed observations of the sun and universal measurements gained by observing distant quasars.
The LFC measures the frequency of light by color. LFCs are caused by a continuously pulsating laser that emits light comprised of millions of different colors that span the entire visible spectrum.
Due to varying frequencies, the colors are separated and form a "comb-like" graph. The comb is used as a ruler to measure the frequency of light from objects like lasers, atoms or stars.
"The performance of this scheme is compared to a sequence of alternating comb and sunlight, and to absorption lines from Earth's atmosphere," wrote the paper's authors. "We also show how the method can be used for radial-velocity detection by measuring the well-explored 5 min oscillations averaged over the full solar disk. Our method is currently restricted to solar spectroscopy, but with further evolving fiber-injection techniques it could become an option even for faint astronomical targets."
"An important aspect of our work is that we use a single-mode fiber, which takes advantage of the wave nature of light to enable a very clean and stable beam at its output," said Rafael Probst, researcher from the Max Planck Institute of Quantum Optics, according to the press release. "This type of fiber is quite common in telecom and laser applications, but its applications in astronomy are still largely unexplored. The LFC at the solar telescope on Tenerife is the first installation for astronomical use based on single-mode fibers.
"Our results show that if the LFC light and the sunlight are simultaneously fed through the same single-mode fiber, the obtained calibration precision improves by about a factor of 100 over a temporally separated fiber transmission.
"We then obtain a calibration precision that keeps up with the best calibration precision ever obtained on an astrophysical spectrograph, and we even see considerable potential for further improvement."
The technique can not only be used to study stars in our solar system, but it can be used to observe Doppler shifts (the sway of stars due to planetary orbits) in stars at a distance. The "wobble" causes the star's speed, therefore, light spectrum to change.
Researchers hope that an LFC could help astronomers spot exoplanets - Earth-sized, habitable planets. "In astronomy, LFCs are still a novelty and non-standard equipment at observatories," Probst said, according to the press release. "This however, is about to change, and LFC-assisted spectroscopy is envisioned to have a flourishing future in astronomy. Our present work shows how future astronomical LFCs could be utilized."
Funding for the project was provided by Leibniz Association, Chinesisch-Deutsches Zentrum für Wissenschaftsförderung and Chinese Academy of Sciences.
