Combining laser frequency combs and iodine cell calibration techniques for Doppler detection of exoplanets
Name
77394T_1.pdf
Description
Main article
Size
2.13 MB
Format
Adobe PDF
Checksum (MD5)
81a0a0e9cf6fb32964e35227b3ac0d27
Author(s)
Cahoy, K.
Fischer, D.
Spronck, J.
Demille, D.
Date Issued
2010
Publisher
SPIE - The International Society for Optical Engineering
Citation
Cahoy, K., Fischer, D., Spronck, J., & DeMille, D. (2010). Combining laser frequency combs and iodine cell calibration techniques for Doppler detection of exoplanets. Proceedings Of The SPIE - The International Society For Optical Engineering, 7739(12 pp.). doi:10.1117/12.858202
Abstract
Exoplanets can be detected from a time series of stellar spectra by looking for small, periodic shifts in the absorption features that are consistent with Doppler shifts caused by the presence of an exoplanet, or multiple exoplanets, in the system. While hundreds of large exoplanets have already been discovered with the Doppler technique (also called radial velocity), our goal is to improve the measurement precision so that many Earth-like planets can be detected. The smaller mass and longer period of true Earth analogues require the ability to detect a reflex velocity of ~10 cm/s over long time periods. Currently, typical astronomical spectrographs calibrate using either Iodine absorptive cells or Thorium Argon lamps and achieve ~10 m/s precision, with the most stable spectrographs pushing down to ~2 m/s. High velocity precision is currently achieved at HARPS by controlling the thermal and pressure environment of the spectrograph. These environmental controls increase the cost of the spectrograph, and it is not feasible to simply retrofit existing spectrometers. We propose a fiber-fed high precision spectrograph design that combines the existing ~5000-6000 A Iodine calibration system with a high-precision Laser Frequency Comb (LFC) system from ~6000-7000 A that just meets the redward side of the Iodine lines. The scientific motivation for such a system includes: a 1000 A span in the red is currently achievable with LFC systems, combining the two calibration methods increases the wavelength range by a factor of two, and moving redward decreases the 'noise' from starspots. The proposed LFC system design employs a fiber laser, tunable serial Fabry-Perot cavity filters to match the resolution of the LFC system to that of standard astronomical spectrographs, and terminal ultrasonic vibration of the multimode fiber for a stable point spread function.
Subjects
astronomical techniques
Doppler shift
extrasolar planets
Fabry-Perot interferometers
laser beam applications
visible spectrometers
MIT Department
Space Telecommunications Astronomy and Radiation (STAR) Lab
Massachusetts Institute of Technology. Department of Aeronautics and Astronautics
Persistent DSpace Link
