Ph.D Thesis


Ph.D StudentEyal Schwartz
SubjectAstronomical Observations of Remote Planets
DepartmentDepartment of Physics
Supervisor Dr. Ribak Erez
Full Thesis textFull thesis text - English Version


Abstract

The search for planets orbiting other stars includes the possibility to eventually find and identify habitable worlds. The thousands of known exoplanets and planet candidates are extremely diverse in terms of their masses or sizes, orbits, and host star type. Naturally the most interesting will be an Earth-like planet whose investigation could add deeper meaning to our own evolution and origins. The problem of detecting and characterizing such a planet is formidable since it is naturally one of the faintest objects in the night sky. 

An Earth-like extra-solar planet emits light which is ten orders of magnitude fainter than that of its parent star in the visible region and up to six in the mid IR at 10mm wavelength. This is the main problem in spectroscopic analysis of such an exo-Earth. In this work I proposed and investigated a new method of identifying bio-signature spectral lines in light from known extra-solar planets based on Fourier spectroscopy in the infra-red, using an off-center part of a Fourier interferogram only. This results in superior sensitivity to narrower molecular-type spectral bands of typical width of 2.5cm-1 (H2O), which could indicate biological processes in the planet spectrum. Such bands would be absent in the parent star’s spectrum. I supported this idea by numerical simulations of the signal expected from the unresolved planet-star combination. I included photon and thermal noise, and showed the method to be feasible at a luminosity ratio of 10-6 for a Sun-like parent star in the infra-red for a typical exposure time of 24 hours. I carried out laboratory experiments using a breadboard optical zero-shear interferometer where I could measure a spectral source in the presence of a black body lamp 105 brighter. I also carried out observations on the 1m Wise telescope to illustrate the method on stars. The results suggest that this method should be applicable to real planet searches.