Laser 'ruler' holds promise for hunting exoplanets
This is a Vacuum Tower Telescope in Tenerife. Credit: Prof. Wolfgang Schmidt
In a paper published today, 18 February, in the Institute of Physics and German Physical Society's New Journal of Physics, the team of researchers have successfully demonstrated how a solar telescope can be combined with a piece of technology that has already taken the physics world by storm–the laser frequency comb (LFC).
The accompanying video abstract can be viewed here.
It is expected the technique will allow a spectral analysis of distant stars with unprecedented accuracy, as well as advance research in other areas of astrophysics, such as detailed observations of the Sun and the measurement of the accelerating universe by observing distant quasars.
The LFC is a tool for measuring the colour–or frequency–of light, and has been responsible for generating some of the most precise measurements ever made. An LFC is created by a laser that emits continuous pulses of light, containing millions of different colours, often spanning almost the entire visible spectrum.
When the different colours are separated based on their individual frequencies–the speed with which that particular light wave oscillates–they form a “comb-like” graph with finely spaced lines, or “teeth”, representing the individual frequencies.
This “comb” can then be used as a “ruler” to precisely measure the frequency of light from a wide range of sources, such as lasers, atoms or stars.
In their study, the researchers, from the Max Planck Institute of Quantum Optics, the Kiepenheuer Institute for Solar Physics and the University Observatory Munich, performed an analysis on the Sun by combining sunlight from the Kiepenheuer Institute's solar telescope in Tenerife with the light of an LFC. Both sources of light were injected into a single optical fibre which then delivered the light to a spectrograph for analysis.
Lead author of the study Rafael Probst, of the Max Planck Institute of Quantum Optics, said: “An important aspect of our work is that we use a single-mode fibre, which takes advantage of the wave nature of light to enable a very clean and stable beam at its output. This type of fibre 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 fibres.
“Our results show that if the LFC light and the sunlight are simultaneously fed through the same single-mode fibre, the obtained calibration precision improves by about a factor of 100 over a temporally separated fibre 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.”
Indeed, the researchers envisage using the new technique to not only study the star at the centre of our solar system, but stars much further away from us, particularly to find Earth-like planets that may be orbiting around them.
When a planet orbits a star, the star does not stay completely stationary, but instead moves in a very small circle or ellipse. When viewed from a distance, these slight changes in speed cause the star's light spectrum to change–a process known as a Doppler shift.
If the star is moving towards the observer, then its spectrum would appear slightly shifted towards the blue end of the spectrum; if it is moving away, it will be shifted towards the red end of the spectrum.
The researchers believe that an LFC would allow them to measure these Doppler shifts much more accurately and therefore increase the chances of spotting Earth-sized, habitable planets.
With conventional calibration techniques, the researchers state that they could measure a change in speed of roughly 1 m/s over large time periods; an LFC could enable measurements with an accuracy of 1 cm/s.
“In astronomy, LFCs are still a novelty and non-standard equipment at observatories. 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,” Probst concludes.
###
The work is a collaboration comprising the Max Planck Institute of Quantum Optics in Garching, Germany, the Kiepenheuer Institute for Solar Physics in Freiburg, Germany, and the University Observatory Munich in Munich, Germany. Among the contributors are guest scientists from the National Astronomical Observatories of China in Beijing. Menlo Systems GmbH in Martinsried, Germany, is part of the collaboration as an industrial partner.
From Wednesday 18 February, this paper can be downloaded from http://iopscience.
Notes to Editors
Contact
1. For further information, a full draft of the journal paper or contact with one of the researchers, contact IOP Press Officer, Michael Bishop: Tel: 0117 930 1032 E-mail: michael.bishop@iop.org For more information on how to use the embargoed material above, please refer to our embargo policy.
IOP Publishing Journalist Area
2. The IOP Publishing Journalist Area gives journalists access to embargoed press releases, advanced copies of papers, supplementary images and videos. In addition to this, a weekly news digest is uploaded into the Journalist Area every Friday, highlighting a selection of newsworthy papers set to be published in the following week. Login details also give free access to IOPscience, IOP Publishing's journal platform. To apply for a free subscription to this service, please email Michael Bishop, IOP Press Officer, michael.bishop@iop.org, with your name, organisation, address and a preferred username.
Comb-calibrated solar spectroscopy through a multiplexed single-mode fibre channel
3. The published version of the paper 'Comb-calibrated solar spectroscopy through a multiplexed single-mode fiber channel' (R A Probst et al 2015 New J. Phys. 17 023048) will be freely available online from Wednesday 18 February. It will be available at http://iopscience.
New Journal of Physics
4. New Journal of Physics publishes across the whole of physics, encompassing pure, applied, theoretical and experimental research, as well as interdisciplinary topics where physics forms the central theme. All content is permanently free to read and the journal is funded by an article publication charge.
IOP Publishing
5. IOP Publishing provides publications through which leading-edge scientific research is distributed worldwide.
Beyond our traditional journals programme, we make high-value scientific information easily accessible through an ever-evolving portfolio of books, community websites, magazines, conference proceedings and a multitude of electronic services.
IOP Publishing is central to the Institute of Physics, a not-for-profit society. Any financial surplus earned by IOP Publishing goes to support science through the activities of the Institute.
Go to ioppublishing.org or follow us @IOPPublishing.
Access to Research
6. Access to Research is an initiative through which the UK public can gain free, walk-in access to a wide range of academic articles and research at their local library. This article is freely available through this initiative. For more information, go to http://www.
The Institute of Physics
7. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.
We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
In September 2013, we launched our first fundraising campaign. Our campaign, Opportunity Physics, offers you the chance to support the work that we do.
The German Physical Society
8. The German Physical Society (DPG), with a tradition extending back to 1845, is the largest physical society in the world with more than 59,000 members. The DPG sees itself as the forum and mouthpiece for physics and is a non-profit organisation that does not pursue financial interests. It supports the sharing of ideas and thoughts within the scientific community, fosters physics teaching and would also like to open a window to physics for all those with a healthy curiosity.
Media Contact
All latest news from the category: Physics and Astronomy
This area deals with the fundamental laws and building blocks of nature and how they interact, the properties and the behavior of matter, and research into space and time and their structures.
innovations-report provides in-depth reports and articles on subjects such as astrophysics, laser technologies, nuclear, quantum, particle and solid-state physics, nanotechnologies, planetary research and findings (Mars, Venus) and developments related to the Hubble Telescope.
Newest articles
Compact LCOS Microdisplay with Fast CMOS Backplane
…for High-Speed Light Modulation. Researchers from the Fraunhofer Institute for Photonic Microsystems IPMS, in collaboration with HOLOEYE Photonics AG, have developed a compact LCOS microdisplay with high refresh rates that…
New perspectives for material detection
CRC MARIE enters third funding period: A major success for terahertz research: Scientists at the University of Duisburg-Essen and the Ruhr University Bochum have been researching mobile material detection since…
CD Laboratory at TU Graz Researches New Semiconductor Materials
Using energy- and resource-saving methods, a research team at the Institute of Inorganic Chemistry at TU Graz aims to produce high-quality doped silicon layers for the electronics and solar industries….