Observational efforts in the last decade revealed that exoplanetary atmospheres are ubiquitously veiled by clouds/hazes that greatly impact observable atmospheric spectra as well as atmospheric properties (e.g., temperature) themselves. It remains highly uncertain how those exotic particles form, what physical/chemical properties they have, how they interact with a background atmosphere, and how they affect atmospheric observations. I have tackled these questions using a microphysical model of cloud/haze formation.

Relevant papers:

• Ohno & Okuzumi (2017), A Condensation-coalescence Cloud Model for Exoplanetary Atmospheres: Formulation and Test Applications to Terrestrial and Jovian Clouds

• Ohno & Okuzumi (2018), Microphysical Modeling of Mineral Clouds in GJ1214 b and GJ436 b: Predicting Upper Limits on the Cloud-top Height

• Ohno, Okuzumi & Tazaki (2020), Clouds of Fluffy Aggregates: How They Form in Exoplanetary Atmospheres and Influence Transmission Spectra

• Ohno & Kawashima (2020), Super-Rayleigh Slopes in Transmission Spectra of Exoplanets Generated by Photochemical Haze

• Ohno & Tanaka (2021), Grain Growth in Escaping Atmospheres: Implications for the Radius Inflation of Super-Puffs

James Webb Space Telescope (JWST) has started to explore exoplanetary atmospheres and revolutionize our understanding on their physical and chemical properties. I am joining JWST Transiting Exoplanet Community Early Release Science (ERS) team and MANATEE MIRI-NIRCam GTO team to facilitate the interpretation of beautiful JWST data from modeling perspective.  

Relevant papers:

• JWST Transiting Exoplanet Community Early Release Science Team (2023), Identification of carbon dioxide in an exoplanet atmosphere

• Feinstein, Radica, Welbanks, Murray, Ohno, et al. (2023), Early Release Science of the exoplanet WASP-39b with JWST NIRISS

• Alderson, Wakeford, Alam, Batalha, Lothringer, et al. (incl. K.O.) (2023), Early Release Science of the exoplanet WASP-39b with JWST NIRSpec G395H

• Rustamkulov, Sing, Mukherjee, May, Kirk, et al. (incl. K.O.) (2023), Early Release Science of the exoplanet WASP-39b with JWST NIRSpec PRISM

• Ahrer, Stevenson, Mansfield, Moran, Brande, et al. (incl. K.O.) (2023), Early Release Science of the exoplanet WASP-39b with JWST NIRCam

• Bell, Welbanks, Schlawin, Line, Fortney, et al. (incl. K.O.) (2023), Methane throughout the atmosphere of the warm exoplanet WASP-80b

Chemistry is a main driver of shaping the observable atmospheric spectrum. For properly extracting the information of bulk atmospheric compositions such as C/O and N/O ratio, it is necessary to understand atmospheric chemistry. I have worked on analyzing a photochemical model to establish a comprehensive understanding on the link between bulk compositions to "observable compositions" of upper atmospheres.

Relevant papers:

• Ohno & Fortney (2023), Nitrogen as a Tracer of Giant Planet Formation. I. A Universal Deep Adiabatic Profile and Semianalytical Predictions of Disequilibrium Ammonia Abundances in Warm Exoplanetary Atmospheres

• Ohno & Fortney (2023), Nitrogen as a Tracer of Giant Planet Formation. II. Comprehensive Study of Nitrogen Photochemistry and Implications for Observing NH3 and HCN in Transmission and Emission Spectra

• Tsai, Lee, Powell, Gao, Zhang, et al. (incl. K.O.) 2023, Photochemically produced SO2 in the atmosphere of WASP-39b

Atmospheric circulation controls the energy transport and thus temperature of observable atmospheres. The circulation could be greatly different from that of conventional tidally-locked synchronized exoplanets once the planets orbit far way from the central star. Planetary obliquity is one of the critical parameters of such non-synchronized exoplanets, as it induces the seasonality in the circulation. I worked on studying the thermal structures of such tilted exoplanets using a 2D shallow water model.

Relevant papers:

• Ohno & Zhang (2019), Nitrogen as a Tracer of Giant Planet Formation. I. A Universal Deep Adiabatic Profile and Semianalytical Predictions of Disequilibrium Ammonia Abundances in Warm Exoplanetary Atmospheres

• Ohno & Zhang (2019), Atmospheres on Nonsynchronized Eccentric-tilted Exoplanets. II. Thermal Light Curves

Several exoplanets are known to have peculiar properties, such as anomalously low apparent density and extremely steep spectral slope in transmission spectrum, which standard theory struggles to explain. One potential solution for those observations is the presence of circumplanetary ring, like what all giant planets in the solar system retain. I have developed a framework to compute the atmospheric spectrum of ringed exoplanet and applied the model to several peculiar exoplanets.

Relevant papers:

• Ohno & Fortney (2022), A Framework for Characterizing Transmission Spectra of Exoplanets with Circumplanetary Rings

• Ohno, Thao, Mann, & Fortney (2022), A Circumplanetary Dust Ring May Explain the Extreme Spectral Slope of the 10 Myr Young Exoplanet K2-33b

• Alam, Kirk, Dressing, Lopez-Morales, Ohno, et al. (2022), The First Near-infrared Transmission Spectrum of HIP 41378 f, A Low-mass Temperate Jovian World in a Multiplanet System

Thermal structure of protoplanetary disk is a key to control the compositions of formed planets. Recent ALMA observations revealed prevalence of ring-like sub-structure, hinting the prevalence of dust trap in protoplanetary disks. Such dust trap was suggested to cast shadow on the disk to greatly alter the temperature. I have worked on modeling the thermal and chemical structure of such shadowy disk and found that the shadow may explain the peculiar atmospheric compositions of Jupiter in our Solar System.

Relevant papers:

• Ohno & Ueda (2021), Jupiter's "cold" formation in the protosolar disk shadow. An explanation for the planet's uniformly enriched atmosphere

• Notsu, Ohno, Ueda, Walsh, Eistrup & Nomura (2022), The Molecular Composition of Shadowed Proto-solar Disk Midplanes Beyond the Water Snowline

More results are (hopefully) coming soon!