11:15 AM - 11:30 AM
[MIS07-07] On the possibility of detecting thermal emission of non-transiting temperate rocky exoplanets without direct imaging
Keywords:Exoplanets, Planetary Atmospheres, Habitability
More than 10 Earth-mass, potentially temperate planets have been identified so far. Among them. Trappist-1 planets, the transiting ones closest to Earth, have been the golden targets for detailed characterization thanks to their well-constrained radii as well as the applicability of transit transmission/eclipse spectroscopy. However, most of the other potentially habitable planets in the solar neighborhood were discovered by the radial velocity method and are not found to be transiting. Methods to characterize these non-transiting planets are required for increasing the number of samples of potentially habitable planets.
Our poster will discuss the possibility of identifying the features in thermal emission of temperate rocky planets in the combined star and planet light. This may be feasible for those around low-mass (i.e., faint) stars thanks to the improved contrast between the planet and the stars in the mid-infrared (> 100 ppm). Thus, we take Teegarden’s star b orbiting an M7 star located at 3.8 pc as an illustrative example. Firstly, with the JWST capability in mind, we study broadband thermal phase curves (i.e., thermal emission as a function of the orbital phase) based on the 3-dimensional atmospheric structures calculated with GCM ROCKE-3D, taking account of the unknown orbital inclination and considering different atmospheric scenarios. We argue that the small phase curve amplitudes at low orbital inclinations could be partly compensated by the increased expected value of the planetary radius, and that the variation may be detectable with the JWST mid-infrared filters (e.g., at 18 um) if the atmospheric pressure <~ 10 bar, in a wide range of inclination. Once the variation is detected, spectral signatures may be used to constrain atmospheric compositions. Secondly, we examine the detectability of the spectral features of atmospheric species using the Doppler shift of the planetary light. We show that the molecular line widths of temperate atmosphere stars can be comparable to or broader than the Doppler shift due to the planetary orbital motion, and thus the signals tend to be self-subtracted and weakened. Yet, the intensive use of large telescopes may be able to provide evidence of atmospheric features.
Our poster will discuss the possibility of identifying the features in thermal emission of temperate rocky planets in the combined star and planet light. This may be feasible for those around low-mass (i.e., faint) stars thanks to the improved contrast between the planet and the stars in the mid-infrared (> 100 ppm). Thus, we take Teegarden’s star b orbiting an M7 star located at 3.8 pc as an illustrative example. Firstly, with the JWST capability in mind, we study broadband thermal phase curves (i.e., thermal emission as a function of the orbital phase) based on the 3-dimensional atmospheric structures calculated with GCM ROCKE-3D, taking account of the unknown orbital inclination and considering different atmospheric scenarios. We argue that the small phase curve amplitudes at low orbital inclinations could be partly compensated by the increased expected value of the planetary radius, and that the variation may be detectable with the JWST mid-infrared filters (e.g., at 18 um) if the atmospheric pressure <~ 10 bar, in a wide range of inclination. Once the variation is detected, spectral signatures may be used to constrain atmospheric compositions. Secondly, we examine the detectability of the spectral features of atmospheric species using the Doppler shift of the planetary light. We show that the molecular line widths of temperate atmosphere stars can be comparable to or broader than the Doppler shift due to the planetary orbital motion, and thus the signals tend to be self-subtracted and weakened. Yet, the intensive use of large telescopes may be able to provide evidence of atmospheric features.