Obliquity of an Earth-like planet from frequency modulation of its direct imaged lightcurve: mock analysis from general circulation model simulation
Abstract
Direct-imaging techniques of exoplanets have made significant progress recently, and will eventually enable to monitor photometric and spectroscopic signals of earth-like habitable planets in the future. The presence of clouds, however, would remain as one of the most uncertain components in deciphering such direct-imaged signals of planets. We attempt to examine how the planetary obliquity produce different cloud patterns by performing a series of GCM (General Circulation Model) simulation runs using a set of parameters relevant for our Earth. Then we use the simulated photometric lightcurves to compute their frequency modulation due to the planetary spin-orbit coupling over an entire orbital period, and attempt to see to what extent one can estimate the obliquity of an Earth-twin. We find that it is possible to estimate the obliquity of an Earth-twin within the uncertainty of several degrees with a dedicated 4 m space telescope at 10 pc away from the system if the stellar flux is completely blocked. While our conclusion is based on several idealized assumptions, a frequency modulation of a directly-imaged earth-like planet offers a unique methodology to determine its obliquity.
Keywords
Cite
@article{arxiv.2006.11437,
title = {Obliquity of an Earth-like planet from frequency modulation of its direct imaged lightcurve: mock analysis from general circulation model simulation},
author = {Yuta Nakagawa and Takanori Kodama and Masaki Ishiwatari and Hajime Kawahara and Yasushi Suto and Yoshiyuki O. Takahashi and George L. Hashimoto and Kiyoshi Kuramoto and Kensuke Nakajima and Shin-ichi Takehiro and Yoshi-Yuki Hayashi},
journal= {arXiv preprint arXiv:2006.11437},
year = {2020}
}
Comments
29 pages, 18 figures, accepted for publication in ApJ