| Abstract: |
Thanks to advancements in observational technologies and the progress of missions, more than 5,000 exoplanets have already been detected. Among them, several planets are classified as terrestrial planets based on their mass-radius relationship. The search for life in the universe is recognized as a major interdisciplinary challenge that spans astronomy, planetary science, physics, and biology. In this context, the study of habitable planets in exoplanetary systems has become an active area of research.
Conventionally, a habitable planet is defined as a terrestrial planet with a functioning internal-surface material cycle that can sustain liquid water on its surface for extended periods. The concept of the habitable zone has been used to guide such discussions. The habitable zone is defined as the range of distances from a central star where a planet can maintain liquid water on its surface; its inner edge is determined by the onset of the runaway greenhouse state, while the limit of greenhouse warming defines its outer edge.
Current research on habitable planets primarily focuses on determining the boundaries of the habitable zone. However, most of these studies are based on Earth’s planetary parameters, and our understanding remains limited for the wide variety of planetary properties observed among exoplanets. In recent years, studies using three-dimensional general circulation models (GCMs) have begun to emphasize the importance of spatial heterogeneity in water vapor and clouds. In particular, a key focus of upcoming observational missions is characterizing the surface environments on tidally locked terrestrial planets around low-mass M-dwarfs. These efforts include investigating not only surface temperature distribution but also the redistribution of energy from the day-side to the night-side. Therefore, it is essential to advance our quantitative understanding of the individual subsystems that constitute the climate system - such as the atmosphere, oceans, land distributions, and clouds - under exoplanetary climate conditions.
In this presentation, I will review the current state of research on habitable planets within the rapidly evolving field of exoplanetary science and discuss both our current understanding and the challenges that lie ahead.
|
